Painting "20/20 vision" by Pat Rawlings, courtesy of NASA illustrates search for life on Mars. I've used a detail from this painting for the cover of this book.

Original caption: "Did life ever exist on Mars? If so, the best evidence may be fossils preserved in the rocks. Geologists and biologists will one day explore Mars, piecing together the history of the planet and perhaps its ancient life".

This is what many will think is what Curiosity should be doing, searching for fossils. Break open a rock and find a fossil, or discover ancient fossilized bones on the surface. 

However, astrobiologists don't focus much on this approach as multicellular life developed only late on Earth. Also when you go to the most inhospitable regions of Earth similar to those on Mars you find only microbial life. Single cell microbes can survive in conditions more extreme than almost any multi-cellular life. There may be lichens on Mars but that is as far as they go by way of realistic hopes for present day multicellular life there. As for past life and fossils, Mars was hospitable enough to encourage multicellular life only briefly for a few hundred million years. Was that enough? On the other hand the climate was constantly changing, with warmer and colder periods and since multicellular life on Earth really took off after "snowball Earth" (or perhaps "slushball Earth"), could that mean that there were factors that encouraged rapid evolution on early Mars?

I said in the intro, if Mars life evolved to creatures with a skeleton, such as fish, then they should be easy to spot. However, if it is a soft bodied creature such as is preserved in the Burgess shales, before the creatures with backbones evolved, then that's far more of a challenge. It may be possible if it finds clay of the right type. This study suggests that rocks rich in berthierine, are ideal for preserving soft bodied fossils. This is a mineral that forms in tropical settings with the sediments rich in iron.

Then there is the possible evidence of microbial mats, perhaps even fossils, and there are enthusiasts who search Curiosity for potential fossils. Perhaps even the 'blueberries' that Opportunity found so many of were concretions created by life. If so we have seen widespread evidence of life on Mars - but we don't yet know how to interpret it confidently. For more on this see my

• How would we recognize fossils on Mars?
• "Blueberries" - Mars equivalent of Moqui marbles - are they signs of past life on Mars?

We may find fossils. It might be that we need to find the "magic mineral" on Mars to spot them. On Earth one key to discoveries of early life was the realization that gunflint chert is a "magic mineral" that preserves traces of early life in exquisite microscopic detail.

• Are there any "magic minerals" to preserve microbes from early Mars?

It is possible we find fossils on Mars. It is possible we've found them already. But the big problem with fossils is to find optimal conditions for preservation - and then also - to be able to recognize them.

POSSIBLE FUTURE FRUSTRATION FOR WOULD BE SPACE COLONISTS

This is especially frustrating for enthusiasts for space colonization who want to send astronauts to Mars. If there is life there and it is vulnerable to Earth microbes - well the worst case is that you have to choose between astronauts and extraterrestrial microbes. 

Now the answer may seem obvious at first, who cares about microbes? But extra terrestrial microbes on Mars? That could be the biggest discovery in biology in recent times. Not only finding life there - but studying it and learning how it works. Let's look at some of the possibilities, and I'm going to have a bit of fun by comparing the language of genes with spoken languages.

• It might be DNA and RNA based but using a different 'language'. For instance the bases might be interpreted as proteins differently. There are thousands of amino acids the bases could be translated into, and the same translation table is used for all life. A human, slime mold, oak tree, lobster with its chitin exoskeleton, pond scum, squid (with its three part brain -two optic lobes and central ganglion) or a silica wall enclosed diatom - within all that variety they all use the same translation table and the language is also the same in many other minute details in every single cell, with only minor variations.
  
  The language in all these organisms is so similar that you can transfer a gene with instructions for making carotene from a fungus into an aphid and it will still make carotene, using the same biochemical pathways in the aphid as it used in the fungus.
  
  A modern biologist is a bit like a linguist trying to understand languages when the only language they have any evidence of is Basque (say). Think how it could expand biology to find a second language in use on Mars (I chose the Basque language here, as it is noted for being a language isolate, unrelated to any other living language). For the very first time they could do the equivalent of comparative linguistics and learn a bit about how biology works with more than one example to compare.
   
• It might be a distant cousin with unexpected capabilities that uses DNA, RNA, the same coding language and is identical in all respects, or almost identical, but diverged billions of years ago. Maybe it evolved photosynthesis independently from Earth for instance (it's especially hard for photosynthetic life to survive transfer on meteorites from Earth to Mars). We have three main variations on photosynthesis - It's a natural corollary from Charles Cockell's paper The Interplanetary Exchange of Photosynthesis. He shows that it's especially hard for photosynthetic life to be transferred between the planets, On Earth we have at least two independently evolved forms of photosynthesis as the haloarchaea work similarly to the light receptors at the back of our eyes, converting light directly into a proton gradient - not related in any way at all to chlorophyll based carbon fixation or the sulfur bacteria. To continue the language analogy - this would be like finding a new dialect, e.g. for the first time you come across Cockney with rhyming slang.
   
• Perhaps it's a distant cousin that diverged so long ago that there are significant differences in how its genetic code works. This would be as if the only language we'd ever come across is US English and then we suddenly come across UK English and learn about how two languages can diverge from each other in details of spelling pronunciation, new words etc. Or it might be like discovering old English or middle English for the first time ever, and beginning to get some hints about how our language originated and developed for the first time.
   
• It might not be based on DNA at all. There are many other ways of building a 'biopolymer'. There's a whole alphabet soup of them, XNA is the general word. PNA, TNA etc. To take the languages analogy - it's a bit like finding a language where there are no vowel sounds or consonants, and instead there are just hisses and clicks, or perhaps musical tones with slides.
   
•  It might be a very early form of 'almost life' that hasn't yet mastered exact reproduction, such as an 'autopoetic cell' that reproduces but only approximately so and hasn't yet developed any way to make sure the daughter cell is an exact copy. With the language analogy - a bit like finding people who haven't yet learnt to speak but have a form of communication that communicates more than animals do with a series of grunts and shouts.
   
• It might be an early form of life that has exact reproduction but is much more primitive. Modern DNA life is far too complex to arise in one go. Earlier life must have been simpler, used fewer chemicals, used only one chemical chain for replication instead of the two RNA and DNA, maybe didn't have proteins. One suggestion is "RNA world " - cells that use RNA on its own for reproduction, and may not have needed proteins, instead using chopped up bits of RNA joined together in various ways. This is like finding an early form of language which only uses the present tense (say), and all the sentences consist of three words, subject, object and verb (in some fixed order)

Also, there are many other places we can send humans, for our first steps in space settlement, the Moon to start with. 

Inside look at one of the ideas for the ESA moon village, using 3D printing on the Moon for the radiation shielding. Image credit Foster + Partners / ESA. Their new director, Professor Johann-Dietrich Woerner is keen on taking us back to the Moon first, and has an exciting vision for a lunar village on the Moon as a multinational venture involving astronauts, Russian cosmonauts, maybe even Chinese taikonauts.

It's a private public partnership as well. Anyone can join in, and contribute habitats, astronauts, rovers and instruments for them to use to explore the Moon, or whatever it is that interests them and suits their capabilities. I think ESA's lunar village is the most exciting idea in human space exploration that we've seen for a long time.

The Moon is cool. Did you know, if you build a swimming pool on the Moon (may be possible if it does have lots of ice at the poles), you'd be able to do leaps like a dolphin out of the water, and a fit person could run fast enough to "run on water" like a Basilisk lizard. See this hilarious XCD about lunar swimming. That may seem trivial - but I think fun is important and part of what makes us civilized myself. We might even have innovative olympics, and new forms of ice skating on the Moon. What kind of leaps and acrobatics could ice skaters do on the Moon I wonder?

This is the ESA video about ideas for small robotic missions first, followed by Antarctic base type settlements on the peaks of (almost) eternal light at the lunar poles.

What's the great rush to send humans to Mars? If there is native life on Mars, many would say we should either leave Mars to the Martians, even if they are only microbial - keep any microbes away and only send sterile rovers there - or at least, study it carefully for some time to learn the priceless secrets it may have to give to us, before we decide what to do next.

COULD MARS LIFE BE IDENTICAL TO EARTH LIFE?

Robert Zubrin, a keen Mars colonization enthusiast, space engineer, and founder of the Mars Society, has said he thinks there is life on Mars and that it is just like Earth life in the same habitat. But, with all his qualifications, still, he is no astrobiologist and that is just an opinion. He gives his reasons with a lot of confidence, enthusiasm and panache. His meteorite argument for instance may seem to be compelling (the idea that meteorites must have taken Earth life to Mars already), until you look into it in detail, when you find it's not as clear cut as it seems.

Most astrobiologists say they have no idea what we could find there, if there is life on Mars. It could be related, or unrelated, but when designing experiments to search for life, we shouldn't assume anything about it. 

WHAT IF MARS LIFE IS LIKE THE TINY 'CELLS' IN THE MARS METEORITE ALH84001? COULD BE VERY VULNERABLE TO MODERN EARTH MICROBES

The only evidence we have so far is from some Mars meteorites that some thought contained life, especially one called ALH84001. If the tiny structures in it are life they may be some form of early life, as they are too small to contain all the machinery of modern life. For a while this seemed rather likely, but then scientists came up with alternative explanations. So, we don't know if it is life or not. But if it is life, it may be RNA world microbes or some other very early form of life, helping to fill the gap in our knowledge between non living chemicals and modern DNA. 

That meteorite is made up of rock that formed billions of years ago on Mars. Still, Mars quickly dried up and got cold with only occasional spells of habitability after that, so maybe it hasn't evolved much since then.

So one form of life we could find there is a very early form of life. If so - there must be some reason why it is no longer here on Earth. We have no evidence at all of any earlier form of life. That might suggest it is vulnerable to extinction by whatever made it extinct here on Earth.

This becomes especially acute when you realize that a human expedition to Mars brings  not just humans (we aren't the problem here), but trillions upon trillions of microbes. On our skin, in our hair, in our stomachs, our food, the air, the water we drink, covering our instruments, our clothes, every square millimeter of the interiors of our spaceships, even the exterior (many can survive exposure to a vacuum). They are everywhere. And what's more there are extremophiles, microbes that do just fine in the most hostile conditions, everywhere too. And the landing on Mars is very dangerous, everyone says that. So a crash of a human occupied spacecraft is a definite possibility, scattering the debris over hundreds of kilometers. After that, it would be the end to any attempt to keep Earth microbes out of Mars, if there are any habitats at all for them to inhabit.

The debris field for Space Shuttle Columbia, with a debris track around 350 miles long, and about fifty to a hundred miles wide (depending on whether you measure to the most distant debris). An accident, especially if it happened early during the supersonic retropropulsion entry to the Mars atmosphere, could scatter debris over a large area of Mars.

SEARCHING FOR LIFE ON MARS IS HARD

So, with people like Elon Musk and Robert Zubrin dead keen to send humans to Mars as quickly as possible, and even the Planetary Society also behind them too, why don't we know the answer to this basic question? Why does nobody know if there is life on Mars or not, or how it relates to Earth life if it is there? 

Well to start with, it's hard. Mars is far away, it costs millions through to billions of dollars to send things there, and the spacecraft we send to Mars keep crashing because it is such a tough place to land. Russia has yet to send a single spacecraft that lasts for more than a few minutes on the surface. The UK Beagle failed because it didn't open all of its solar panels - so near and so far. The ExoMars Schiaperelli lander crashed. NASA has lost spacecraft too such as the Mars polar lander. It's far harder than the Moon because of its thin atmosphere, and high gravity. Not enough atmosphere to just use a parachute to slow down. But too much gravity to use retrorockets (as for a lunar landing) without relying on the atmosphere to slow you down. And with such a thin atmosphere, the landing sequence is over quickly, within minutes.

Even if you had humans "on site", it would happen too fast for them to react in time to sort out most issues. Then you also have the latency delay which is so much that if Earth got notification of an error at the start of the landing sequence, the whole thing would be over before any correction could arrive at the spacecraft. It's on its own to complete a complex automated sequence of aeroshell jettisoned, parachutes opened then jettisoned, and then retrobraking or airbags, or other soft landing method where fractions of a second count,. The whole thing has to be completed flawlessly in minutes.

All landings on Mars so far started with an aeroshell and aerobraking to slow down in the upper atmosphere. Next comes the parachute, because it would just take so much fuel to do all the rest of the slowing down using rockets. But a parachute can't slow you down enough for a landing, because the atmosphere is so thin. So then you have to find a way to slow your spacecraft down even further, from those hundreds of miles an hour to a slow enough speed for a soft landing. This shows the sequence for the Schiaperelli entry, as it was supposed to happen.

See Schiaperelli: the ExoMars Entry, Descent and Landing Demonstrator Module

I think it would be fair to say that no other landing attempted in our solar system is as complex, and time critical at so many possible points of failure as a landing on Mars. It's also dependent on weather - though the atmosphere is so thin, it's also highly variable in density, with huge pressure changes from day to night, and also it is often loaded with the dust from Martian duststorms when our spacecraft arrive there. You don't know what the exact conditions will be until your lander hits the atmosphere, and the landing sequence has to be auto adjusted on the fly when it gets there to cope with whatever conditions it finds.

And the Mars surface is also on the very edge of hospitality. If it was totally inhospitable, like the Moon, then it would be easy to show that there is no life there. If it was as hospitable as the Earth you'd find life in the first scoop of soil (as they rather optimistically hoped would happen with Viking). But - it's just on the edge. It's got a thin atmosphere, but just enough for some salty brines to form. It's got ice and where you've got ice and salt, then water can form. It's just warm enough for life to be barely possible. If it is there, then it's probably only just hanging on. Microbes in patches here and there, maybe metabolizing so slowly they have lifetimes of thousands of years (if you go by the most similar habitats on Earth). Any life is probably huddled inside rocks, or beneath a thin layer of dust, or it could be in a thin layer of fresh water trapped a few centimeters below a surface layer of clear ice. 

It's not going to be visible from orbit, unless it releases significant amounts of gas into the atmosphere (but remember it's probably only very slowly metabolizing in the cold conditions there). And a rover may well not find it either - not easily. Don't expect to see bunny rabbits hopping around on Mars. Or trees or bushes. It's no "Barsoom". But what's more, it's possible that most of Mars is uninhabited. It may have large areas of total desert, more inhospitable than any desert on Earth, with a few patches of life here and there as tiny smudges of a thin film of microbes. Not much to look at but they could be the most extraordinary microbes ever found. Inside they may be extraterrestrials, a different biology, like a whole new ecosystem inside. It's like all our life we have only ever been able to study the African savannah, and for the first time we find a coral reef. That's how different the inside of a Martian microbe cell might be, as compared to all the lifeforms any biologist has ever seen on Earth. It would be an utter tragedy to lose such a thing, if it's there, before we even know it is there.

Even so - we've sent lots of missions to Mars. Surely we have a first idea of whether there is life there or not? Surely we could at least say whether there is life in the sand where Curiosity is driving?

Well, no. We can't even answer that. Nobody can say for sure even if there are microbial spores or dormant states in the dust that Curiosity photographs every day. It's just not equipped to answer such questions.

It's partly because it is just so difficult to look for life there. But it's also partly because we are not really looking for life in the right way. And we know that, at least the astrobiologists do, and have been saying so for decades. 

NOT FOR LACK OF TRYING BY ASTROBIOLOGISTS

The astrobiologists have been asking for new missions to search for life there ever since Viking. Many of them.

A team of astrobiologists in the US built the UREY instrument for ExoMars which would have been a capable life searcher but then the US pulled out of the collaboration with ESA and the instrument was dropped - years and years of work, just leading to nothing.

Of course that is common in the space community - but the difference here is that NONE OF THE ASTROBIOLOGY INSTRUMENTS FOR MARS EVER FLY.

Many geological and geochemical instruments never fly either but we do get SOME GEOLOGICAL INSTRUMENTS SENT TO MARS.

There are many new instruments that can be sent to Mars. They are getting smaller and lighter with every year.

ESA nearly included Life Marker Chip, mass of 4.7 Kg, in their proposed ExoMars payload - a very capable and innovative life detector for alien biology using polyclonal antibodies but that also was descoped. There are many more they can send.

Astrobionibbler, the replacement for UREY has shrunk down to a small instrument you can hold in your hand - target mass 2.5 Kg. What's more, it is so sensitive now that it can detect a single amino acid in a gram of a sample.

Dallas Ellman fine tunes a component of the astrobionibbler. It uses ideas from the larger UREY instrument, using high temperature high pressure subcritical water as a solvent for non destructive extraction of organics. However, with advances in technology, it's now miniaturized to a "lab on a chip". During his summer internship at JPL in 2014, he helped discover and replicate the conditions the Astrobionibbler team needed to extract and detect amino acids from Martian regolith. As a result it is now so sensitive that it could detect a single amino acid in the sample.

New instruments would be even lighter.

There's an end to end gene sequencer now that we could send to Mars based on two commercial components that you can hold in a hand each. It’s called SETG. It's under active development and they think it could be made flight ready within a year last time I checked their publications.

But instead NASA plan to send MOXIE on Mars 2020 (the successor to Curiosity). MOXIE has a payload mass 15 kg, enough for 3 - 6 astrobiology life detector instruments, and does nothing except generate oxygen which is then vented into the Mars atmosphere. It is useless for the rover, as it is just a test for technology they hope to send to Mars eventually to support some human mission there. Mars 2020 doesn't need oxygen. And MOXIE doesn't need to move. And it adds 15 kg it has to carry with it wherever it goes - why couldn't it go on the Insight lander or some other stationary lander?

And that's along with a sample return cache which the astrobiologists have said over and over, in many papers, is not the way to test for life on Mars. Because it would just be pot luck if you get any life in the sample unless you can detect it there.

The most likely predicted outcome is that it returns samples similar to the ALH84001 meteorite and other Mars meteorites we already have with organics and ambiguous possible signs of life that will be argued over indefinitely. The astrobiologists when asked about a sample return say it is not worth the huge expense for almost certainly ambiguous samples that would not significantly advance their subject. They said clearly that this is not the way to advance their subject, yet who listens to them?

The structures in these photos are between 20 and 100 nm across, well below the resolution of a diffraction limited optical microscope of 200 nm. To this day, nobody knows if they are ancient fossil cells or formed by chemical processes on Mars. The astrobiologists warn that even if we test for organics, any samples we return from Mars are likely to be similarly ambiguous, triggering debates that run for decades without resolution. They say the only way to search for life on Mars is to send biosignature detection instruments there. They say that the time to consider a sample return is when all other options have failed - but so far we haven't even started - we haven't sent a single astrobiological instrument to Mars since Viking.

The only astrobiologist to talk in favour of a sample return that I know of is Chris McKay. And he says an elaborate mission like Mars 2020 is far too expensive and not the way to do it. He would just send a simple vehicle to pick up a sample of dust from the surface - as informative as you are likely to get without an in situ targeted search for astrobiology - and return that to Earth. A few days on the surface tops.

I cover this in detail in my section: Astrobiologists advocating strongly for an in situ search on Mars first in the book. I go into the papers by  Bada et al', by Paige, and by Cockell et al all arguing that we need an in situ search looking for biosignatures and life itself in situ before we even consider a sample return - at least if the reason to return the sample is for the purposes of astrobiology.

But for historical reasons, nobody listens to the astrobiologists when planning a “search for life” on Mars. The decadal survey and mission plans have ignored all the astrobiological papers warning against sample returns, The engineers and geologists have made this decision to send this caching rover, which will drill samples and then leave them in cache heaps on Mars, and then a second rover whose only job is to follow in its tracks, pick up one or more caches and take them back to a Mars ascent vehicle and return them to Earth. They prioritize this so high they plan to use the entire budget for the single most expensive 'flagship' project for NASA for not just for the 2010s, but two decades, right through to the end of the 2020s, if the mission is completed.

This decision is based on a decadal survey that in its summing up simply ignored the white paper submitted to it by eight astrobiologists that argued strongly against a sample return saying it would mortgage the budget for Mars missions for 20 years to return samples that would be likely to be as ambiguous for astrobiology as the Mars meteorites we already have.  

All this was ignored in a summing up that said that it was the consensus of the Mars community that a sample return was the most important thing to do and that it was worth setting all other mission suggestions to Mars aside to achieve this. There was a massive disconnect between the white paper and the decadal review summing up.

This could have consequences. The result of this long expensive process and return of samples that cost as much per gram as the most expensive diamonds in the world could easily be a headline like this - this is what the astrobiologists are warning may happen:

The image here is a detail of one of the less well known close up electron microscope photographs of ALH84001, the controversial meteorite that was first announced as the potentially the first discovery of life on Mars, but later the announcement was withdrawn as premature. It remains controversial to this day, with astrobiologists arguing both sides of the case.

I created this fake newspaper story using this online free newspaper generator.

I cover this in the sections:

• What if Mars has really tiny cells - like the structures in the Mars meteorite ALH84001?
• Idea of returning samples from Mars to Earth - how does it compare with an in situ search for astrobiology?

However the decision is made. The design for Mars 2020 is finalized. To add this sample cache, the engineers have had to descope an updated version of SAM (Sample Analysis at Mars) from Mars 2020 to make room for it. This reduces the capability of Mars 2020 to do preliminary analysis of the samples - the very thing the astrobiologists say is the top priority if you want to search for life on Mars.

Indeed they also made an executive decision last year that they won't need to sterilize the sample container 100%. This saves on the engineering complexity, and so, the expense of the mission. As a result it even has a small chance of an intact viable spore from Earth in any of its sample tubes on arrival on Mars. So, just as happens for studies of Mars meteroties that get to Earth, if you find biochemicals there, in trace quantities, then you may find it hard to demonstrate for sure that they came from Mars. Since the sample tubes are not guaranteed to be free of viable spores from Earth, you might even find a viable microbe spore or dormant state in the sample, and culture it, and have no way to discover for sure whether it comes from Mars or Earth.

This is a misconception many Mars colonization enthusiasts have. They think it would be easy to decide if a microbe came from Mars by sequencing its gene. Well if it is an anthrax spore (Robert Zubrin's favourite example) you know for sure it didn't come from Mars. But if it is not in our genes databases for Earth microbes, you know nothing about it either way. It could be from Earth or it could be a closely related distant cousin from Mars. Only 0.00001% of all microbial species on Earth have been sequenced to date. See Largest ever analysis of microbial data (May 2016). And even if it is genetically very similar - do you know for sure that it's not an Earth microbe with a particularly stable genome that somehow got to Mars via panspermia?

The thing is, the decision making process in NASA and the Decadal survey is filled with engineers, geologists and others who have different priorities. They just have different insights from the astrobiologists, who get ignored over and over again. 

MARS COLONIZATION ENTHUSIASTS SAYING OUR CHANCE IS OVER NOW

This is partly driven by enthusiasts who want to try to “colonize” a cold dry airless rock. The air is so thin that your lungs can’t function without a full body pressure suit as the moisture lining your lungs would boil at blood temperature making gas exchange impossible, you wouldn’t last more than seconds. There is no possibility of adapting, it’s simple physics that lungs can’t work at Mars pressure levels. Ordinary Earth plants can’t grow there. At night for 100 days of the two year long ‘year’, even at the equator it still gets cold enough for the carbon dioxide to condense out of the atmosphere as dry ice, along with water vapour, making the temporary morning ‘frosts’ first photographed by the Viking landers.

It’s as easy, some would say easier to live on the Moon than on Mars.

And then, in conversation anyway, some colonization enthusiasts say to those enthusiastic about searching for life on Mars:

"Look we haven't found life yet so let's just go ahead and contaminate Mars, you've had your chance and you blew it".

So, perhaps some of you reading this may think like that. If so, it's not true at all. The physicists and geologists and geochemists are the ones who ‘blew it’, if anyone did, not the astrobiologists.

PHYSICISTS CONSTANTLY SEARCHING FOR MORE AND MORE DETAILED EVIDENCE OF PAST HABITABILITY OF MARS

It's not so much that they don't want to find life. It's more that they have a slow leisurely approach to it. They continue to have as their top and nearly only priority to establish past habitability of Mars in more and more detail, "follow the water", and are showing no signs of moving on to the next stage of looking for life there, except for the idea of returning a sample from Mars, which astrobiologists say, emphatically, is not the way to search for life

It's interesting and useful but astrobiologists have been saying all along we don't need to know the past and present habitability in minute detail before searching for life. We could have been searching for it all along.

And as for habitability, we need to search not just for water but for nitrogen too. We need a "follow the nitrogen". Nobody is doing that particularly.

Also - for present day life, we have never sent anything to the most likely places to find life. Not only that, we don’t have any missions even on the drawing board to search for present day life on Mars. We have many suggestions now for places they may be, but not one mission being planned to go to any of those places.

THE BEST PLACES TO LOOK FOR PRESENT DAY LIFE ON MARS - TOTALLY UNEXPLORED AT GROUND LEVEL

The best places to look include the RSLs - streaks that form seasonally in spring on sun facing slopes when local temperatures reach around 0 C. They grow down slopes in summer, then broaden out and fade away in autumn. Though the dark features aren’t water (this has been known for a long time) bur rather perhaps mini cascades of dust (recent observations) they are associated with hydrated salts. This strongly suggests that at least thin films of briny water may be forming there.

There are many other places to investigate. For instance, this is not widely mentioned outside the specialist literature, but there are some features in Richardson's crater near the south pole called “flow like features” that form in the debris from Martian carbon dioxide geysers, which may be due to liquid water forming below the surface.

Whether that’s what they are or not, modeling shows that any transparent ice in the polar regions should lead to formation of a thin layer cms thick of fresh water below the surface seasonally, forming within days. The main question is whether the transparent ice exists there on Mars - it does on Earth in Antarctica and if the same transparency is achieved on Mars the liquid water layers should exist for the same reason that they form in Antarctica. There at least, there often are layers of fresh water a short way below transparent surface ice. The clear surface ice melts the subsurface layers through the solid state greenhouse effect. If this happened on Mars, the subsurface water would be trapped and so would be liquid and unaffected by the near vacuum of its atmosphere. Liquid water can also form in droplets around grains of dust in clear ice that absorb heat.

Then there are the droplets that can form on salt / ice interfaces rather rapidly anywhere on Mars where there is ice and salt in proximity, a discovery by Nilton Renno’s team (he is the head of the Curiosity team investigating surface conditions on Mars, and the weather station on Mars). This has only been shown in Mars simulation experiments but it may be the explanation of what seem to be droplets of some liquid that formed on the Phoenix lander legs. The Phoenix lander had no way to analyse them and we haven't yet been back to find out what they are for sure, but the smart money is on liquid brines as a result of salt thrown up from the legs as it landed. But were they due to salt / ice interfaces or were they due to deliquescing brine? Nobody knows. And are droplets found like that naturally almost anywhere on Mars or were they some strange result of the Phoenix landing itself? Again nobody can answer for sure but Nilton Renno's experiments suggest they may be common on Mars wherever salts of the right composition touch ice. He calls them "swimming pools for a bacteria".

And then there's the night time humidity that life could exploit without water at all, being explored in many experiments by astrobiologists in Germany. They found that some lichens, and some cyanobacteria, can not only survive but even grow and metabolize in Mars simulation conditions, shielded from the worst of the UV light in partial shade.

If life does survive without water on Mars, then one idea is that it may use a thicker higher humidity layer trapped briefly above the morning frosts - or else some astrobiologists suggest that life could exploit micropores in salt, which in the Atacama desert are able to increase the humidity of the surrounding air significantly, enabling cyanobacteria to live at humidity levels normally considered far too low for life.

There are the methane seeps also. They may or may not be signs of life. If they are due to life then that's definitely life with some communication to the surface. One theory is that it may be generated by life on the Mars surface. There's also the thin layer of water now detected indirectly by Curiosity below its wheels as it drives over sand dunes. We know it is there through humidity measurements. The scientists think it is sometimes warm enough for life but too salty, and sometimes the other way around - but Nilton Renno has suggested that biofilms may be able to exploit it and create conditions for life as life so often does in hostile conditions like that.

What would we learn about life in the Atacama desert or the McMurdo dry valleys in Antarctica if we only had satellite measurements to go by? The life is usually hidden below the surface, undetectable at all from the air, and in Antarctica, there are microbes with lifetimes of millennia, just barely subsisting on the minimal resources there, yet they are alive and of great interest. When returned to a laboratory for study, they can take months just to ‘wake up’ and do something given plentiful resources.

There are so many things the astrobiologists want to test and explore - as well as searching for past life which involves drilling to a depth of at least 2 meters. Ideally 10.

ExoMars will be the first rover sent to Mars with any decent chance of finding evidence of past life there.

Surface organics rapidly degrade with the cosmic radiation over billions or even hundreds of millions of years and you also have a constant influx of organics from meteorites. That incidentally is also why detecting organics in a sample to return to Earth is no guarantee at all that the sample is of interest for the search for life. You need in situ life detection. Or else the chances are you just return organics from comets or meteorites that mimic biosignatures (as we know they can do). Curiosity has already found organics on Mars and it is thought to come from meteorites.

If there is any life in the equatorial desert sands- one of the most unlikely places to find life there but it's not impossible, especially as dormant spores - then neither Curiosity nor Mars 2020 are sensitive enough to spot it. When Mars 2020 collects its samples for return to Earth, there could be traces of present day life just centimeters away from the drill bit, and there would be no way for Mars 2020 to detect it. That's not at all impossible either, since life in hostile conditions is often very patchy with seemingly identical patches of rock some with life and some without.

And it would be tragic to make native life on Mars extinct, or to mix it with Earth life through horizontal gene transfer (if related) or confuse the search.

ZUBRIN'S METEORITE ARGUMENT

I mentioned this in the introduction. It's one of many arguments Zubrin makes that may seem compelling at first. He has argued that Mars life should be identical to Earth life through meteorite transfer.

But even the Chicxulub impact 66 million years ago, though it could send material at escape velocity to Mars, would subject any life to huge shocks. Then, remember, the rocks have to LEAVE THE ATMOSPHERE AT ESCAPE VELOCITY.  Think how fast they have to leave the surface, and rush through the atmosphere, to exit it at a speed of at least 11.2 km / sec, even after slowing down through several kilometers of dense atmosphere.

So, while traveling through the atmosphere at well above 11 km / sec the surface of the rock is going to become hotter than any incoming meteorite and ablate away any photosynthetic life on its surface. All that will survive are maybe some heavily shocked microbes buried deep within rocks - and then when they get to Mars they have to find a suitable habitat on a dry barren planet. How likely is that?

The Chicxulub impact incidentally was into a shallow tropical ocean. Not the most likely place to find microbes that could survive on Mars (though not impossible).

Artist's impression by Don Davis of the Chicxulub meteorite impact into a warm tropical ocean. A huge impact like this could send debris all the way to Mars through our thick atmosphere, and the first rocks would get there even in the first century after the impact on Earth. However they would leave Earth's atmosphere at escape velocity, so any photosynthetic life exposed to the surface as well as the surface of the rock itself would ablate away. The shock to send such rocks all the way to Mars is also huge.

Though some life may have transferred to Mars in this way, it's likely to be especially hard for photosynthetic life. For all forms of life it may have been easiest in the early solar system over three billion years ago, with huge impactors tens of kilometers through to hundreds of kilometers in diameter that created regions of lower acceleration in the crust, so less shock and also formed holes in the atmosphere so that the rocks could escape through a near vacuum to outer space.

It’s far easier for life to get from Mars to Earth in a meteorite, because its gravity is far less and the air is thinner too. But that’s a major challenge also. We get tons of material from Mars every century - but all the material we receive today has spend hundreds of thousands of years in space (since the last impact on Mars able to send materials as far as Earth). They are from only a few occasional glancing impacts on Mars once or twice every million years, and moreover, they are nearly all from the higher southern uplands of Mars with its even thinner than usual atmosphere, about as dry as it gets there, covered in old lava fields, and one of the least likely places to have life on Mars. And to make it worse, the material all comes from at least a few meters below the surface on Mars. Modeling of the crater impacts shows that only subsurface rocks reach escape velocity in these collisions, and also studies of the meteorites themselves show they haven't been affected by cosmic radiation in the way you'd expect from surface rocks on Mars.

Unless the asteroid impacting on Mars happens to hit a geological hot spot, then any life would have to be on the surface, warmed by the sun. It is also likely to be within dust or salt or ice or else just below the surface of rocks. Life like that could never get to Earth in a meteorite because the rock crusts, dust and salt it inhabits can't get transported here.

So far we have no proof that life has ever been transferred in either direction. Models suggest life can be transferred from Mars to Earth especially in the early solar system, but we don’t know if there is life on Mars robust enough to do this, as its capabilities if any are of course completely unknown. That’s the easy direction, and from Earth to Mars it probably only happened during early impacts so large they blew a hole in the atmosphere leaving a vacuum for the rocks to fly through. It’s possible that Earth and Mars life is related, through this process over 3 billion years ago. Or just as possible that it is unrelated.

As I touched on in the introduction, the most vulnerable type of life would be some early pre-cursor of Earth life. Perhaps so early that it hasn’t yet developed the modern two biopolymers system of DNA + RNA, and it may not even have proteins yet. At least, that was one of the theories used to try to explain the tiny potential cells in the meteorite ALH84001 as it permits cells too small for modern life. We don’t yet know if those structures are cells. It’s neither been proved or disproved. We have two alternative models - biological and chemical, and so far no way to decide between them which is why it is not being called a discovery of life. But it could be. More evidence from Mars could end up with a proof that ALH84001 actually does have fossils of early Mars life.

If so - with such cold dry conditions since then, perhaps it has evolved no further and what we have there still are early RNA world cells, too ancient to have proteins, or DNA. Maybe that is what is present in all the habitats on Mars. This is just one possibility but we can’t rule it out and I like it because it helps show how vulnerable Mars life could be to Earth life. Presumably it would be quickly made extinct by whatever originally made it extinct on Earth, if it is indeed some early Earth life precursor

IDEA THAT YOU HAVE TO SEND HUMANS BECAUSE THEY ARE SO MUCH FASTER AT EXPLORING

Our rovers are so slow on Mars - wouldn't a human speed things up hugely? Well - what's the good in speeding things up if you are just going to find the life you brought there yourself? If as a result you miss the very thing you are looking for, or even make it extinct before you get there (in the case of a crash of a human spaceship bringing Earth microbes to the planet)?

But as well as that, I think we got a false idea of the possible speed of robotic exploration of Mars because of the  low bandwidth, as well as the latency lag.

Perhaps as our robots return to the Moon and we control them from Earth, and get confidence at driving them around faster on the Moon we may start to see a far more rapid remote exploration, similar to exploration of ships on the sea bed using remotely controlled robotic submersibles. Also when we get the long awaited broadband upgrade for communications with Mars with a dedicated communications satellite there, perhaps in the mid 2020s, with 800 gigabytes of information a day,  - we might find that makes an amazing difference too. 

There are other developments coming too. Far better autonomy based on the recent research on self driving cars, robotic dogs, etc. There is no reason why a rover on Mars can't travel as fast as, e.g., the lunar rover, which operated on similar terrain on the Moon.

Then, there's artificial real time - a technique from on-line gaming that lets you work with a time delay and latency far better by using a model of the scene you are exploring and the other actors in the scene on your own computer, and using physics models to extrapolate what is going to happen before it happens. Perhaps we will see this first for exploration of the Moon, and then on Mars. And then finally, humans in orbit around Mars, exploring the surface with close to real time telepresence

Once we see how much faster the rovers can be on the Moon and later on Mars - able to travel tens of kilometers a day for instance, then maybe there will be less frustration about the limitations that would follow from keeping Mars free of Earth microbes for now, for planetary protection reasons.

ROBOTS CAN BE STERILIZED AS MUCH AS YOU LIKE - EVEN 100% STERILE

This is another challenge we have to face before we can search for present day life - to find a way to sterilize the spacecraft adequately. Curiosity is exploring not far from a feature that may possibly indicate an RSL - a brine seep. However it is not sterilized sufficiently to go close enough to "taste it". It will probably have to stay at least several kilometers away. How do we sterilize a modern spaceship sufficiently to study these habitats? We haven't yet found a way to sterilize an icebot sufficiently to visit Lake Vostok in Antarctica, the lake cut off from the surface possibly for millions of years - so this may be a challenge if it is indeed a liquid water / brine habitat.

The current recommendation is to sterilize to the levels of the Viking lander - but that still had an estimated 30 viable spores on the spacecraft - and those are cultivable spores with potentially a hundred times that number of viable dormant states that can't be cultivated. Is that adequate if parts of the rover can directly contact liquid water instead of the dry surface encountered by Viking?

We actually have the technology for 100% sterile landers on the horizon. All we need to do is to find conditions that no biological organisms can withstand, but that electronic components can. There are several possibilities there but one of the most promising is to use heat. We now have high temperature electronics that were not available in the 1970s and many high temperature materials as well, and even cameras and other instruments designed to work at very high temperatures This is partly because of the need for various terrestrial applications (e.g. in engines) and also there's been a fair bit of work into high temperature components for a Venus lander and rover.

There is even one already proposed as an icebot to drill into Europa. It would be heated to 500 C throughout the long journey out to Europa - and can do that by using an RTG instead of a battery and other components that can tolerate being kept at high temperatures for months on end. Should we press ahead with that, and aim for 100% sterile landers before we explore the RSLs and the possible liquid water habitats in Richardson crater etc?

I discuss this further in my book under Can we achieve 100% sterile electronics for an Europa, Enceladus, Ceres, or Mars lander?

VALUE OF UNINHABITED MARS - NEAREST SUCH FOR LIGHT YEARS IN ANY DIRECTION

Even if Mars is uninhabited but has uninhabited habitats - it is our one and only chance to study uninhabited habitats on a terrestrial planet. There are many possibilities for habitats in icy moon oceans but Mars is our only chance outside of Earth for a habitat in a surface environment with liquid water and an atmosphere.

That's far more important than you might think. Uninhabited habitats with organics, water, nitrogen etc but no life could tell us what happens on planets similar to Earth and Mars in our galaxy that don't have life. 

Do they form cells? Self replicating chemicals? Just organics with nothing even remotely resembling life? What happens to a terrestrial planet like ours, with organics, after billions of years, if it doesn't evolve life? This is our only chance to find out.

MARS COLONIZATION ENTHUSIASTS COULD DESTROY ALL THIS BY MISTAKE, NOT EVEN KNOWING IT IS THERE

As most of us know Elon Musk is dead keen to set up a city on Mars. He plans to send many copies of his BFR until there's a city of a million there with his rocket so big it forms instant mini skyscrapers immediately on landing on Mars. 

Elon Musk's idea is to start shuttling colonists to Mars in 2024 with the aim of building a city of a million there using his BFR - "Big Falcon Rocket". This shows it at an early stage, with three of them landed on the surface.

To get the scale of his ambition - each of those rockets is 48 meters high and 9 meters in diameter. That's a 14.5 story skyscraper - he has three skyscrapers on the surface there, and that's just the start. Those skyscrapers shuttle back and forth between Earth and Mars in his plans, constantly delivering colonists and supplies and goods to Mars.

He is known for delivering late - so maybe he won't get there in the 2020s. But he recently successfully launched his Falcon Heavy, a rather spectacular achievement in an almost picture perfect launch that looked almost indistinguishable from the CGI. So who knows, maybe he can achieve it eventually? Well what then happens about the search for astrobiology on Mars, and planetary protection, if someone starts to build a city of a million there? Especially if some of the spaceships crash, as they easily could, as they come in to land on Mars, the most perilous landing in our solar system to date.

It's a bit hard to see how colonists on Mars could thrive for long without billions of dollars support, or more likely trillions of dollars, a year, from Earth. But if he does develop his BFR, he will have the ability to get them there at least. I think it's not so clear who would pay for their spacesuits, habitats etc once they arrive on Mars.

Aside on spacesuit costs: at present spacesuits cost two million dollars each, and would take someone who has all the skills two and a half years to build, given all the components to hand. They are also good for only a couple of dozen space walks and need servicing. It currently costs $100,000 per astronaut just to fit the airtight bladder inside their gloves to help reduce the risk of them losing their fingernails as a result of the stiffness of the gloves, and to make the gloves a bit more comfortable. Okay prices will go down, but they are going to need some serious levels of income just to pay for their spacesuits, and that's just one of many items that would be essential for a prospective Mars colonist.

The Planetary society too, lead by Bill Nye, are dead keen to see humans on the Mars surface by the 2030s. They take a slightly more cautious approach saying we should explore Mars from orbit first. But (at least in an interview), Bill Nye sees the landing on the surface as the very next mission after the orbital mission, two years later. How could that be enough of an exploration of the Mars surface to be sure that you know already whether or not there is life on Mars or know the impact of humans on it, or indeed, of it on humans, if it is detected?

They could blow all that away for what? Impatience to get humans to Mars as soon as possible.

Well, what can we do about that? I'm writing this as a keen space flight enthusiast myself. Thrilled when I watched Apollo 11 land on the Moon aged 14 in July 1969. I'd love to see humans adventuring in space. But responsibly. We have to find a way to do this that is compatible with scientific integrity and our wish to learn about the biology of forms of life that maybe based on different principles from ours.That's just as important I think.

Well - if only the enthusiasm can be redirected somehow. And there is an obvious place to direct all this human spaceflight enthusiasm and that's the Moon.

THE MOON AS OUR NEIGHBOUR AND NATURAL PLACE TO EXPLORE FIRST ON FOOT

The Moon is there right at hand for us to explore with minimal planetary protection issues. Far safer for humans. At the moment the ISS always has 'lifeboats' attached that can return all the crew to the Earth in hours, in event of some emergency (e.g. a meteorite hits the ISS). On the Moon, we can have similar 'lifeboats' fully loaded with food, oxygen, fuel, everything needed to get everyone back comfortably to Earth in two days.

If we go as far afield as Mars, we need lifeboats that are reliable that can take the entire crew back to Earth in six months. Or much longer than that if Earth is in the wrong place for a fast transfer, as it usually will be.

For many reasons, the Moon is the obvious first place to go to. Many astronauts have said that. Even Buzz Aldrin, who is so keen on Mars, says we should go to the Moon first (Obama took his quote out of context when he said 'Been there, done that' - it was intended by him as a facetious joke).

The retired Canadian astronaut Chris Hadfield, former commander of the ISS, thinks that the voyage of humans to Mars is for the next generation of astronauts. Interviewed by New Scientist, he put it like this in their article "We should live on the moon before a trip to Mars"

"I think ultimately we’ll be living on the moon for a generation before we get to Mars. If the world and the moon were threatened and the only way to preserve our species was to launch from Earth, we could go to Mars with yesterday’s technology, but we would probably kill just about everybody on the way."

"It’s as if you and I were in Paris, paddling around in the Seine in little canoes saying, 'We’ve got boats, we’ve got paddles, let’s go to Australia!' Australia? We can barely cross the English Channel. We’re sort of in that boat in space exploration right now. A journey to Mars is conceivable but it’s still a lot further away than most people think."

Are these canoeists on the Seine ready to head off with their paddles and open canoe to Australia? 

We have only sent a few people there for up to three days at a time for less than a decade starting in 1969. We have explored only a few spots in equatorial regions on the near side of the Moon. Only one scientist has ever been there, a geologist, on one expedition, and the rest were all test pilots with some basic training in geology. It’s barely explored. Our explorations from orbit have turned up many surprises. And we can expect many more as we explore the surface. It may even have evidence of life from Earth, Mars, even Venus in early meteorites trapped for billions of years in the polar ice still with organics preserved in a deep freeze far colder than any freezer on Earth for all that time.

It has many advantages over Mars for humans. Including near 24/7 solar power at the poles, probable ice at the poles, the vast lunar caves and importantly - at least some potential of commercial exports to Earth.

CLOSE TO ZERO COMMERCIAL POTENTIAL FOR MARS

Mars has just about zero commercial potential. Robert Zubrin's idea from the "Case for Mars" of exporting deuterium doesn't work at all if you try to fill in the details. It is only slightly concentrated on Mars, by only one step of numerous ones used on Earth for the full process. You need a thousands of tons factory to concentrate it further. There's no way that importing deuterium from Mars could be worth the cost of offsetting just a few steps of concentration in a 27,000 tons deuterium factory on Earth, the size of a skyscraper, and powered by a large hydro-electric scheme with an output of 128 MW.

Elon Musk echoing Robert Zubrin says Mars colonists would pay for their colony by export of intellectual property to Earth. That they would make so many amazing inventions in those hostile conditions that they would fund the colony by licensing them to us on Earth. Some find that argument plausible - I find it deeply implausible myself. What about all the inventions from Earth they are using on Mars?

And what if someone else does become a multi-billionaire from an invention he or she makes on Mars? What’s to stop them coming back to Earth to enjoy their billions, with Earth likely to seem a luxury planet to them after Mars. Take early retirement to a tropical island in the Pacific, an absolute paradise after Mars and buy yachts and private jets and whatever else they fancy from the billions they earned from the inventions they made on Mars.

And only one in a million perhaps does that. Do they pay for million dollar, or even hundred thousand dollar replacement spacesuits for all their comrades on Mars to mention just one item of expense in a space colony? They would need to be benevolent trillionaires to do that.

Even if you optimistically assume a huge export of inventions in only the one direction from Mars to Earth, how is that supposed to pay for a space colony exactly? Sorry, I don't get it.

AT LEAST SOME COMMERCIAL POTENTIAL FOR THE MOON

With the Moon there's the potential of exports of platinum, of ice, there's possible tourism, even one week trips from Earth, And much of it is unexplored. There's the hard vacuum and unoxidized surface which means you have pure iron there instead of iron oxide and you have ideal conditions for making electronics sh as natively deposited solar cells with a vacuum far harder than any used in factories here on Earth. The CO2 is mainly an asset on Mars for making oxygen and methane fuel from hydrogen feedstock with the Sabatier reaction or you can also electrolyse it directly.

Well you need far less fuel for returning materials fron the Moon to Earth, as the return delta v is so low. Also the Moon has ice at its poles in large quantities, and it may be easy to extract. If so, you can electrolyze the ice to make hydrogen and oxygen, making the Moon a source of fuel too, which you can use to fuel rockets, but also export to LEO.

Also because the Moon is at a constant distance from Earth you can travel there at any time,. You also,have the possibility of using two momentum exchange tethers that together are able to exploit the difference in gravitational potential from the Moon to Earth to send materials from the lunar surface to hypersonic flight in the Earth upper atmosphere. This uses existing materials such as Kevlar (it's not like the space elevator) and works a bit like a waterwheel, and actually generates power needing almost no use of fuel at all. It is powered by the flow of materials from the Moon to Earth. That's Hoyt's cislunar tether system which would pay for itself in mass savings after just one year of operation with one mission a week to the Moon. I think it deserves rather more attention than it gets. For more on this, see my

• Exporting materials from the Moon in my online and kindle book: Case For Moon First: Gateway to Entire Solar System - Open Ended Exploration, Planetary Protection at its Heart

MOON IDEAL FOR A BACKUP

And the Moon is an ideal place to set up a backup if that is your main reason for going into space. There is almost nothing could make us extinct anyway - humans are far more hardy and robust, with minimal technology than most give us credit for. We are amongst the least at risk of extinction species on our planet. We can survive anywhere from the Kalahari desert to Siberia and the high Arctic with minimal technology. With fire, clothing, shelters that we build, ability to cultivate crops, keep animals, even living off shellfish, we could survive just about anything. At least some of us.

If you want a backup - well you can backup seeds on the Moon. Ideal for that, permanent temperatures in the lunar caves just right for a seed bank. Add a small colony exploring self sufficiency in space and you have the best backup you could have right close, as close to Earth as you can get. What would you do if Earth was devastated? Try to build a civilization on Mars? Of course not, your top priority would be to return to Earth as soon as possible and rebuild a civilization here. It’s always going to be the most habitable place for humans in our solar system. A backup is used to restore the original - that’s the whole point.

We don't need to be multi-planetary - what good does it do to be spread thin over two planets and to have massive megaprojects with planet sized thin film mirrors or 500 half gigawatt factories just making greenhouse gases for a thousand year project of uncertain outcome on Mars - think what those same levels of funding could do in cislunar space!

Terraforming is just a step too far at present. We couldn't even terraform a duplicate of Earth with a thick carbon dioxide atmosphere without life, oxygen or nitrogen in the atmosphere with any confidence of success, never mind Mars. Meanwhile you can set up a city dome or Stanford Torus or O'Neil cylinder anywhere. There's enough material in the asteroid belt for radiation shielding and other materials for habitats with a thousand times the land area of Earth. You could never build a thousand copies of Mars but you have materials there to build habitats with similar land area.

It is just so wasteful to terraform a planet. Create a kilometers thick atmosphere (with a buffer gas such as nitrogen as well as oxygen) in order to generate 2-3 meters thickness of breathable air at the surface. Fill hundreds of meters or kilometers depths of dry sand with water in order to have a bit of moisture in the atmosphere so you can grow plants (when with aeroponics you need hardly any water at all)

OTHER LOCATIONS FURTHER AFIELD

If you want to go further afield, with Elon Musk's BFR you could go to Callisto, say. Masses of ice, well outside Jupiter's radiation belts. Great place for exploring deep space settlements.

This has no planetary protection issues as far as we know, and it has resources of value to us too.

Artist's impression of a human exploration base on Callisto, the outermost of Jupiter's four largest moons, and its second largest moon after Ganymede. Image from page 22 of NASA's vision for space exploration, 2004. For details of the mission design, see this paper.

There's Venus too and its upper atmosphere. There's Mercury with its polar ice.

We could send humans to orbit around Mars too and to operate instruments and rovers on the surface by telepresence.

Why send humans as quickly as possible to the one place in the inner solar system most vulnerable to contamination

SO WHAT IS OUR BEST CHANCE OF FINDING LIFE ON MARS IN THE NEAR FUTURE?

I think the chance of Mars 2020 making a significant astrobiological discovery is minimal. They simply didn’t listen to the advice of the astrobiologists when planning the mission.

I'm most hopeful for ESA actually. They have more of an interest in astrobiology currently than NASA. In the sense of following recommendations of astrobiologists about how to search for life there.

At least ExoMars is going to drill 2 meters which astrobiologists have been saying for many years is a top priority - but again got ignored. NASA is going to send the Insight lander to drill 5 meters for geology but no interest in doing that for an astrobiology mission.

It has a chance of finding past life, while Mars 2020 has next to none of finding either past or present day life, if the astrobiologists are right as I think they are from what I've read. And then in future they may send more capable rovers with astrobiology in situ instruments.

Imagine for instance, how embarrassing it will be for NASA if the first astrobiology instrument sent to Mars by ESA or maybe even the ISRO or something discovers that there are spores widespread in the dust in small quantities and that their rovers could have found it decades ago if they had but followed up the Viking experiments?

That is Gilbert Levin's view. Now, I’m not saying he is right, but he hasn't been proved wrong either. He could have been proved wrong in any of the follow up missions since Viking if they had sent an updated version of his experiment or other astrobiological instruments to test for life in the dust. But nobody ever did.

Our rovers could be traveling over spores of life in the dust every day. Nobody would know yet.

In the very near future I think our best bet is ESA's TGO (Trace Gas Orbiter) which is in orbit around Mars right now and will soon start its science phase. First instrument dedicated to astrobiology for observation of the Mars atmosphere ever. It is very sensitive to biological gases in the atmosphere. It may be able to pinpoint sources of methane and perhaps other gases of interest to the search for life also. Not certain it does as life at concentrations similar to the Atacama desert and McMurdo dry valleys would have negligible effects on the atmosphere but if there rae higher concentrations it may well detect them.

FAST EXPLORATION OF THE SURFACE OF MARS

So what about sending humans to the surface? It’soften argued that we could explore far faster in person.

But what is the point in landing on Mars and finding life quickly, if what you discover is life that you brought there yourself? Especially if you get a human spaceship crash on Mars - that's the end of any planetary protection of Mars.

There is a spectacular mission we can do instead of a surface mission that has the same or even more potential for exploring Mars with no risk at all of contaminating what you are studying with Earth microbes. At least if you do it carefully (you need to be certain, of course, that your insertion burn can't crash the spacecraft into Mars - I wonder if an alternative might be to use "ballistic transfer" and ion thrusters once you get to Mars to get into the right orbit, slower but safer).

The idea is to go into a sun synchronous orbit similar to a Mars capture orbit. You approach the sunny side of Mars twice for each Martian day, each time the opposite side of Mars. So you get to see the entire planet from orbit every day. It's an inclined orbit, a Molniya style orbit, so you get to fly close to the polar caps too, and go past both poles, every day too, twice a day each.

Imagine the view! From space Mars looks quite home-like, and the telerobotics will let you experience the Martian surface more directly than you could with spacecraft. You'll be able to touch and see things on the surface without the spacesuit in your way and with enhanced vision, and adjust the colours to show a blue sky also if you like. It's like being in the ISS, but orbiting another planet.

12th April 2011: International Space Station astronaut Cady Coleman takes pictures of the Earth from inside the cupola viewing window.- I've "photoshopped" in Hubble's photograph of Mars from 2003 to give an impression of the view of an astronaut exploring Mars from orbit.

This is a video I did which simulates the orbit they would use. I use a futuristic spacecraft as that was the easiest way to do it in the program I used to make the video. Apart from that, it is the same as the orbit suggested for HERRO.

It would be a tremendously humanly interesting and exciting mission to explore Mars this way. The study for HERRO found that a single mission to explore Mars by telepresence from orbit would achieve more science return than three missions by the same number of crew to the surface - which of course would cost vastly more. Here is a powerpoint presentation from the HERRO team, with details of the comparison.

That’s only one study. But there have been no other attempts at a comparison study between exploring Mars by telepresence and exploring it in situ as far as I can see. So it is all we have to go for. Shouldn’t that comparison be made before making major decisions? That was some years back, for the HERRO plan for studying Mars via telepresence in a sun synchronous Mars capture orbit. Telerobotics has moved forwards enormously since then. What would a present day study conclude?

Our current robots there are very slow - but Opportunity did in 10 years what took Lunakhod 2 just a few months by way of travel. The improvement in technology since the 1970s lead to a rover that is more than 50 times slower. Why? Because of the longer time delay between Earth and Mars and the low bandwidth for communications and lack of opportunity to communicate (typically they send instructions to the Mars rovers around once a day).

With modern technology we should be able to operate rovers on the Moon that travel far faster even than Lunakhod 2. Even Lunakhod 3 would have been significantly faster. With autonomy and high bandwidth we could have much faster rovers on Mars even when operated from Earth and when operated from low Mars orbit they would be far faster again. Thera's no reason why our rovers on Mars, even operated from Earth, and with the level of autonomy shown by modern ‘self driving’ robots, shouldn't travel as fast as the lunar rover, tens of kilometers a day or more, even tens of kilometers an hour.

There is no reason apart from a lack of dedicated satellites in Mars orbit why they can’t return multiple gigabyte microscopically exact 3D panoramas of their entire environment multiple times a day which scientists on Earth could then explore at their leisure in 3D, looking at nearby rocks so closely it’s like using a geologist’s magnifying lens. What difference will this do even to exploration of Mars from Earth?

Yes let’s send humans into space, to the Moon, where there are minimal planetary protection issues. Meanwhile the search for life on Mars has only barely begun. Let’s do this responsibly and be sure to avoid the tragedy to go there only to discover life we brought there ourselves.

EXCITING FUTURE

I’m excited to think what we may find there in the near future.

I'm keen on humans in space, but I think we should start with the Moon and try also humans on Callisto, the asteroid belt, the moons of Mars, Mercury's polar ice, and (assuming it remains consistent with planetary protection as some astrobiologists think there is a small chance of life in the clouds of Venus) the upper atmosphere of Venus,.

But I think that we shouldn't be in a hurry to send humans as fast as possible to the surface of Mars, the one place most vulnerable to Earth microbes in the entire inner solar system. Not until we know more.

I have written three books on this topic - this is the latest, available to read for free online, or you can buy it for Kindle.

You can read my Touch Mars? book free online here:

Touch Mars? Europa? Enceladus? Or a tale of Missteps? (equivalent to 1938 printed pages in a single web page, takes a while to load) also avilable on Amazon kindle

The other ones are

• Case For Moon First: Gateway to Entire Solar System - Open Ended Exploration, Planetary Protection at its Heart - and on kindle
• MOON FIRST Why Humans on Mars Right Now Are Bad for Science - and on kindle.
  This includes my An astronaut gardener on the Moon

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