How do you deal with the trash on the Moon? This is not an exciting or glamorous subject I know, but it is part of the reality of space travel. This is something that's easy to forget about, how much trash astronauts generate every year. We don't notice it so much on the ISS because it is easy for the astronauts to dump it, and it all burns up cleanly in the atmosphere. The Apollo crew didn't spend enough time on the Moon for it to be that noticeable. Also there is nothing else nearby to get contaminated by trash in the ISS, but on the Moon then you want to study the geology of the area around your base, and there may also be ices close by if you are at the poles near one of the craters of eternal night. You may be surprised at how much trash the ISS generates. We may have humans back on the moon as soon as a decade from now so it's probably not too soon to start thinking about this in earnest.

In such challenging conditions we are bound to have wastes of all sorts pile up around the base. This is how much refuse the Progress rockets return to Earth, to burn up in the atmosphere:

See all that trash which you can see filling up those white bags in this video? The ISS discards that much trash into our atmosphere every few months. Now imagine all of that piling up around a base on our Moon, or later on as our astronauts get there, on tiny Phobos or Deimos? 

The Moon would be a great place to see what happens to all that trash, and find out what are the best ways to deal with it before it becomes an issue further away. We should be able to find a solution with vast landscapes covered in regolith, easy to dig. But we may learn a lot while discovering how best to handle the trash.

How much can we recycle? Or do we just bury it all? Some of it is "smelly stuff". For instance on the ISS the astronauts don't have facilities to wash their clothes. As soon as their socks, smalls, shirts etc begin to get a bit smelly or dirty they just put them into a bag and eventually it ends up burning up in the Earth's atmosphere at a very high temperature, along with the Progress vehicle itself.

On the Moon, all those bags will pile up around their base unless they find another way to deal with the trash. They would recycle what they can of course, but that might not be easy in such challenging conditions. How do you recycle a spacesuit that doesn't work any more for instance? They will have quite an incentive to find a way to do some recycling. Washing their clothes makes sense, but that's not the easiest of things to do in a spaceship. 

Washing machine for the ISS designed for the UMPQUA research group but I don't think it ever flew. Currently astronauts wear their clothes once and then throw them in the trash and they get burnt up in the atmosphere 

Incinerate most of it in an oven??

A base on the Moon surely isn't going to send all its trash back to Earth. It's not like the Progress attached to the ISS. You need 1.6 km / sec delta v to launch it as a payload from the Moon into orbit, and if you were to send it back to Earth to burn up in our atmosphere, you'd need another kilometer per second for a Trans Earth Injection. You would use up a lot of good fuel to burn your trash in Earth's atmosphere. They surely won't do that. If there are ships shuttling back and forth between the Moon and LEO they'd either return empty (with less fuel) or take something useful back from the Moon to LEO. So your base would have piles of trash build up around the base.

Then the thing is that, like the Apollo 11 footprints, any trash you leave on the surface of the Moon will still be there thousands, and probably millions of years into the future. It won't degrade, rust away, and mix into the landscape.

Then you have the astronaut footprints too. Maybe it's just aesthetic - but the landscape around any Moon base would soon get covered in overlapping footprints in all directions towards the nearby horizon.

Buzz Aldrin standing near a leg of the lunar module - notice how many footprints they left on the Moon? These will still be there a million years from now.

It will be the same for the area around any lunar base. It will soon be totally covered in footprints - unless they either turn the dust around the base to glass or they rake the soil. In the same way, all the trash they leave on the surface of the Moon will also still be there a million years from now too.

It would be the same for a base on tiny Phobos or Deimos. Also any other small region such as the most favoured "peaks of almost eternal sunlight" at the lunar poles.

It's the same for any geographically small region of the Moon, for instance the region around a lunar lava tube cave entrance (unless they put all the trash into the cave?). It will soon be covered in footprints and trash after humans have been there for a few months / years. The Moon would be a great place to get a first idea of what the scale of impact of this will be, as we explore the solar system, and to make our first experiments in dealing with this issue and learning what we can do about it.

I can't find much on the problem of trash on the Moon. It's often mentioned in passing but not discussed in detail. But here is an abstract from 1988 which gives a succinct summary of the main issues. 

After describing the main sources of trash including the descent platforms - which remain on the surface when the modules return to orbit, and they estimated as 4.9 tons each, paper, cloth, wood, plastics, ceramics and glass, aluminium and steel, they then go on to describe possible disposal methods, considering landfill in caves, craters, and areas of permanent shade.

The primary disposal process on the lunar surface of the by-products of shredding, wet oxidation or solar furnaces, will be burial. The initial temptation of filling nearby craters will be unavoidable for the initial settlement, but cannot continue for any extended time. As lunar mining becomes a reality, ample landfill opportunities should arise. An alternative to crater filling or direct burial would make use of areas of perpetual shade if available near the colony. These areas, if large enough, exhibit absolute darkness and temperatures near 150 K that would make for excellent limited disposal sites.

Most of that surely still applies, though I'm not sure if piling trash into areas of perpetual shade would be favoured so much nowadays given the interest in any ice or volatiles that might have accumulated there. Perhaps in caves though? Would some of the lava tube caves, or sections of them, be earmarked for trash disposal?

Or perhaps they just dig pits in the regolith and cover them over?

Also much of the trash is a resource. The trash on the Moon will have many materials in it that would be almost impossible to make locally and that would cost a lot to send up from Earth. Recycling would be hard to start with but get easier as they develop more technology and industry on the Moon. Perhaps in the not so distant future our descendants or even our older selves may return to those trash pits from the early twenty first century and mine them for valuable resources. If so it might be worthwhile segregating the trash before burying it to make things a bit easier for the future astronauts on the Moon who wish to re-use it.

Also, though it may seem the best thing to do is to compact it to take up as little space as possible, crushing, and burning it, is that really the best solution? Maybe in the not so distant future, some of the materials may be useful if not incinerated or compacted? 

For instance tanks, or a spacesuit, perhaps equipment that has some small thing wrong with it that the astronauts couldn't fix on the spot with the materials they had - either in the future the astronauts may find a way to recondition them, or to re-use the materials or components for some less demanding task.

These are just a few thoughts on the subject. If anyone reading this knows of good material on trash on the Moon do say!

Rocket exhausts, microbial spores and organics mixing with levitating lunar dust

The Moon is also an ideal place for us to learn lessons to help with protection from Earth microbes in places further afield than the Moon. But on the Moon also, even though our microbes can't survive and reproduce there, the organics from dead microbes can confuse scientific studies of organics on the Moon.

We can study survival of microbial spores in space conditions. For one thing, we can study the spacecraft that have been there for decades, crashed or landed there, to see if there is any viable life on them. This could give us good ground truth on planetary protection. On the same subject see the slides in this powerpoint presentation: Organic Measurements on the Lunar Surface: Planned and Unplanned Experiments

There were some early studies with returned Apollo 11 samples that suggest that it's rare for microbes to remain viable in the lunar surface conditions, however this is with very limited data. First, they estimated that the lunar surface where the Apollo 11 astronauts collected their samples had only 10,000 to 100,000 viable microbial spores from Earth per square meter (between one and ten spores per square centimeter). They did do a few analyses of selected samples from other missions up to Apollo 14 for colony forming spores, inoculating them into with different media, and no colonies formed. 

Here is a detailed description of the process of examining a sample from Apollo 11, no colony forming life was found after inoculating 3,000 petri dishes each with 4 mg of the sample (total of 12 grams). In another paper, one of the four samples they tested was actively biocidal (perhaps heavy metal toxicity) but other soil samples were able to support colony forming spores, but didn't. However, those are only a few analyses of selected samples and with early 1970s technology.

The returned Apollo samples actually highlight the need to take care about contamination of the Moon if we are interested to find out about native organics. A NASA study in 2015 re-analysed some Apollo samples, using modern methods searching for amino acids.

The analysis was a tricky one because there were several ways the amino acids could form (native to the Moon, produced by reactions with rocket fuel contamination in the lab, or from Earth organics).

In the end they decided that most of the organics came from Earth microbes (because of preference of the "left hand" form and the carbon 12 / 13 isotope ratios) but some probably came from meteorites. The samples are now known to have up to 70 parts per billion of organics from life. However much of that could be contamination of the samples after return to Earth (see this paper).

Sadly this is a bit inconclusive, but it does suggest that, even with the Moon we may need to take care to avoid contamination of the samples by Earth organics, either in situ on the Moon, or after return of the samples to Earth, when exploring areas where the amounts of organics on the surface are of scientific interest.

The microbes, rocket fuel, and trash left on the Moon by the Apollo astronauts in a stay of up to three days is nothing to the trash that would accumulate around a human base. So, another thing we can do on the Moon is to find out how much by way of organic contamination and other types of contamination accompanies human explorations, and how far it spreads.

This could be important for a small site, for instance Phobos or Deimos and especially if there is a scientifically interesting site close to the human base where they wish to study organics in material that got there from early Mars (say).

In the low gravity the dust and organics could spread far just by  being kicked off the surface by an astronaut. Indeed you could kick a ball into orbit around Deimos easily, anyone could. and as you walk or hop around Deimos, some of the dust you kick up would go into orbit around it.

For instance the Deimos gravity is only 0.003 m/s² compared to 9.807 m/s² for Earth, so 3269 times weaker. So a throw that would last one second on Earth would last 3,269 seconds on Earth. The distance thrown goes up in the same proportion by s = 0.5 at². So whereas on Earth a bit of dust scuffed by your foot will travel maybe one meter, on Deimos it will travel 3.27 km, or even further given that the surface is curved. Indeed kick a bit faster and the dust will go into orbit.

It's radius is only 6 km. Indeed the orbital velocity for Deimos is 4 meters per second (use 1.4762e15 kg for the mass and 6 km for radius in this orbital velocity equation online - derivation of the equation here for those interested). That's about 9 miles per hour. So you could kick a ball into orbit around Deimos very easily and trash from the base will easily spread to cover the entire moon if we aren't careful.

The dust won't get kicked so far on the Moon. Just six times further than on Earth, or a little further because of the lack of air to slow it down. You could shoot a golf ball 2.5 miles on the Moon, though Alan Shepherd's shot went less than 200 meters, as Robert Pearlman of Collect Space pointed out - the location of both golf balls is known, with one of them photographed from the lunar module window.

So you might think that organics on the Moon would only spread as far as the humans themselves travel, away from the base, and a bit further to allow for dust being kicked up by human feet? Most of it just localized around the base? There are no winds there, no dust storms (like the Moon), no weather at all, right?

Well, yes, of course the Moon doesn't have any weather as we know it, and it doesn't have global dust storms like Mars either. So, the organics won't spread as easily and as far as they do on Mars. However, it does have electrostatically levitated dust, which surprisingly can levitate even particles as large as 140 microns in diameter (line 215 of this paper). The dust is levitated through UV radiation, and plasmas.

A microbe that gets caught up in a 140 nm particle would be protected from UV (though of course affected by the electrostatic discharges that levitate the particles in the first place). So, if you introduce foreign material to the Moon, it could spread some distance in this levitated dust. Perhaps even viable microbes.

But it can travel further and faster as a result of the rocket launches. The rocket exhausts for Apollo 12 disrupted about two tons of dust around the landing site that lead to localized dust storms observed during the next few sunrises as measured from the Apollo 12 landing site levitated to a height of one meter above the ground.

So how far can the dust spread? The finest dust might have gone right up to orbital altitudes. At least, the Apollo astronauts sketched what seem to be rays of sunlight hitting the dust at sunrise and sunset from orbit. However recent observations by LADEE show that there is no dust at altitudes between three kilometres and 250 kilometres. At least not any more, if there was back then.

Lunar horizon glow as photographed from orbit by Clementine spacecraft. The bright dot at the top is Venus and the Sun is behind the Moon. The Moon has an exosphere - an atmosphere so thin that the molecules rarely encounter each other. However LADDEE proved that there is no dust above 3 kilometers.

Since the Moon has a surface area larger than Africa, a few spores spreading out through dust levitation aren't going to do much to confuse science results kilometers away, unless there are habitats for life there. Every indication is that there are no habitats that Earth life could colonize on the Moon. Even ice exposed to the surface temperatures, if it ever sees sunlight or even light reflected from nearby boulders or the landscape, will vaporize quickly, at tens of meters a day at 0 °C in a vacuum (the Apollo astronauts used this to cool themselves down with their ice sublimators). It's only because of the extreme cold conditions, colder than liquid nitrogen, that ice can get trapped in the permanently shadowed craters at the poles.

Some areas of the Moon could be particularly sensitive to organics from Earth. In a review paper from 2007, the authors suggest that perhaps the Moon's categorization for planetary protection may need to be revisited depending on what we find out about the lunar ice. If this ice and the other volatiles there are of especial interest for study of prebiotic chemistry for instance, perhaps we might need to set up "organic special regions" on the Moon that need to be kept free of organics.

"Other locations, like the permanently shadowed craters at the Moon’s south pole, may contain water ice or hydrated minerals and other valuable scientific and physical resources. If, for instance, these sites contain ice with signs of prebiotic chemistry, one can envision the establishment of organic special regions to protect these native lunar organics for careful scientific study."

So, unlike Mars, it's not an issue with replicating life. Just the organics confusing searches. But that may be enough so that we need to set aside special regions to preserve the science interest of some of the ice there. Perhaps they would need to be studied only by sterilized robots if you wanted to do ultra senstiive measurements of the organics in the surface layers of the ice, and especially if it is "fluffy ice" as is one possibility for the lunar ice deposits.

Although the human bases at the poles would be right next to permanently shadowed craters, perhaps the organics wouldn't spread far in the cold desiccated conditions there.

Two tons of dust per landing is quite a lot of dust to send off into the nearby craters, if you are doing ultra sensitive scientific measurements of the organics. On the other hand however, there is no UV light to levitate the dust once it gets into the craters so it may mainly contaminate areas around the edges of the permanently shadowed areas. And much of the surface will be shadowed anyway as the sun is so low close to the horizon. Maybe that will help with the problem of levitated lunar dust at the poles.

Then in addition, there are ideas to turn the dust into glass for a landing pad, so perhaps that would help with the dust too. You could also glaze the areas immediately around the haitat, and perhaps you have glazed boundaries around the special regions to warn astronauts from approaching too closely. Just suggesting a few ideas here.

So, it may not be a major issue, but this is certainly something to study and monitor. It could be an issue for regions that we want to keep free of organics and other contaminants close to a human base.

Luckily there does seem to be plenty of space there to have regions for ice extraction for the base and other separate regions that are kept intact for careful scientific study. And the process of ice extraction itself would be of scientific interest as it would be expected to turn up many meteorites from early Earth, Mars and maybe Venus and Ceres that may have organics preserved all those billions of years at cryogenic temperatures.

If we follow that suggestion to set up regions of special scientific interest to keep free of contamination - there are hundreds of square kilometers of permanently shadowed ice at the poles, an estimated 1,850 square km of ice at each pole .

That's just an estimate though. And the ice might be patchy.

However if the organics do spread beyond the base - well the Moon is an ideal place to study such things. It has minimal planetary protection issues compared to anywhere else. If it does still have some contamination of the polar ice by organics from the human base, well this is a chance to study the situation.

The historical lunar landing sites are another area that may need protection from contamination by Earth microbes. They are valuable for planetary protection scientists,as places to study the effects of a brief human presence on the Moon several decades later. They are a:

"valuable and limited resource for conducting studies on the effects of humankind’s initial contact with the Moon" (quote from page 774 of this paper).

These sites, with microbes exposed to cosmic radiation, UV etc are also decades long unplanned experiments in the interplanetary cruise stage of panspermia - the ability of microbes to remain viable in the conditions of interplanetary space for transfer from one body to another. (see page 771)

Another planetary protection question for the Moon (in its broadest sense) is whether our landers would change the Moon's very tenuous "atmosphere" or exosphere with rocket exhausts. Each Apollo lunar landing added 10 tons of exhausts to the atmosphere with a persistence half life of approximately one month. That might not seem a lot but it is a noticeable amount for the lunar atmosphere which has a total mass of approximately 25 tons.

We have a golden opportunity right now to observe its atmosphere "as is". The rocket exhausts from Apollo should have dissipated long ago. Amongst other things we can study the movement of water vapour in the lunar atmosphere and see where it comes from. Well it will be a while probably before we get humans landing on the Moon again, but we do have man robots due to land there in the near future, including (if they keep to schedule) the remaining Google Lunar X Prize contenders in 2017, and Astrobiotic, in 2018 (they dropped out of the Lunar X-Prize saying the 2017 timetable was unachievable). So what effect will they have on the lunar atmosphere?

Well when the Chinese Chang'e 3 landed on the Moon on 14th December 2013, we had an excellent chance to find out as NASA's LADEE is still in orbit analysing the lunar atmosphere.

Artist's concept of NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) Image Credit: NASA Ames / Dana Berry

They came to the surprising conclusion that the Chinese lander hadn't modified the lunar atmosphere at all, or at any rate, if there were any changes, they were beyond their detection limits They studied it from a distance of 1,300 km so they couldn't observe the dust it kicked up (which only lasted for about 15 seconds in the Chinese descent video). No exhaust products were detected and the lunar atmosphere wasn't changed in any way.

This is good news for robotic missions to the Moon at least. This was a particularly large lunar lander for a robotic mission, so it seems that any effects from rocket exhausts are only local and don't have any global effects on the atmosphere, and the exhaust products don't travel large distances either.

Here is what they said in detail:

"Surprisingly, the LADEE science teams' preliminary evaluation of the data has not revealed any effects that can be attributed to Chang'e 3. No increase in dust was observed by LDEX, no change was seen by UVS, no propulsion products were measured by NMS. Evidently, the normal native lunar atmospheric species seen by UVS and NMS were unaffected as well. It is actually an important and useful result for LADEE not to have detected the descent and landing. It indicates that exhaust products from a large robotic lander do not overwhelm the native lunar exosphere. As the descent video shows, the interval of time that dust was launched by the lander is very short, perhaps less than 15 seconds. LADEE would probably have had to be in just the right place at the right time to intercept it. Also, significant amounts exhaust products apparently cannot migrate to large distances (hundreds and thousands of miles) and linger with sufficient density to be measured. "

What, though, about more local effects on the lunar surface, especially the lunar ice? We don't have any ground data on that yet, but we have some theoretical modeling. This shows the modeled effect of the Apollo 17 landing exhausts on the lunar surface near their landing site:

Figure 28 from this paper showing their modeled rocket exhaust contamination of the lunar surface from Apollo 17 superimposed over Google Moon. The contaminated area spans 522 kilometers of the lunar surface. The red range rings contain 50% and 67% of the total contamination respectively.

There would surely be scientific interest in the organics on the surface of the ice at the lunar poles. This modeling suggests we may need to take care about the effects of rocket exhausts from spacecraft landing in the vicinity of the lunar village, especially once the larger rockets start landing with astronauts on board. So what can we do about this?

The authors of the paper looked at future missions "where contamination by exhaust gases is not desired" and recommended that:

  • Most of the braking is done with the engine pointed over the horizon and with the exhaust gas velocity much greater than the lunar escape velocity.
  • Once the lander has lost enough momentum, its braking engine and excess fuel could be dumped to reduce the landing mass
  • With the lunar lander now lower in mass, it can make the final descent to the surface using less fuel.

Perhaps I can make another suggestion of a way to reduce the exhaust problem even more, once we have frequent travel to the Moon. Hoyt's Cislunar tether transport system. uses counter rotating momentum exchange tethers. At the Moon end of the transport system, the tether can be stationary relative to the Moon's surface whenever it is closest to the Moon, so that you can pick up payloads from the surface and deliver them to the surface with no need to use any rocket fuel to do this.

His lunar tether masses only seventeen times the payload mass, so you don't need that much traffic per year for this to be worth doing, just for economic rather than for planetary protection reasons. Once you get that much mass in orbit around the Moon, from then on, landing on the Moon and taking off again is essentially fuel free, and what's more, you get an automatic boost from the tether to take your spaceship down to LEO. Or indeed you could use the same method to go all the way down to Earth's atmosphere on an Earth return trajectory. This would not only reduce the amount of fuel needed to land on the Moon and take off to essentially zero, and make it more economical to travel to and from the Moon. It would also protect the lunar surface and exosphere from the effects of rocket exhausts. For details see the Exporting materials from the Moon section of my Case for Moon First.

Then, there's another potential benefit for Hoyt's cislunar tether. Perhaps you could dispose of lunar trash in the Earth's atmosphere as for the ISS, after all as there is essentially no cost of fuel to do that. That is, if you wanted to. Perhaps the trash may come to be very valuable on the Moon with much to recycle in it, once they had the capability. They might value the elements and components even, things like screws, sheets of metal etc, even paper, cloth and so on, that would take a lot of work or import costs from Earth to make on the Moon. But if they so wished, with Hoyt's tether, they could dispose of trash from the Moon in the Earth's atmosphere easily. There's a lot to be thought over and worked out here.

In conclusion, the Moon is an ideal place to look into such issues. Before we send humans to Phobos or Deimos or wherever they go next, we'd better know what humans will do to a celestial body when they set up a settlement there. This is especially important if the aim is to study ice deposits in craters, or other sensitive locations. In the case of Phobos, its regolith should have records of organics and even spores of life possibly, from pretty much the entire history of Mars mixed up with it, brought there by asteroid impacts into early Mars. So, it might well be important to keep the Phobos regolith, or parts of it, clean from organics and other contaminants from Earth. Our experiences on the Moon may help to give us the experience we need to design suitable precautions for missions like this.

Protection of the historical Apollo landing sites

Also - the lunar X Prize will have many smaller missions go to the Moon, commercial ones. We may see the first of them towards the end of this year. There are five teams in the competition, SpaceIL plans to use the SpaceX Falcon 9, but it’s had trouble fitting its mission into their faring. Hakuto has made a pact to land with Team Indus and both will use the Indian rockets - it’s proven technology but they are having trouble raising the funding. Moon Express will launch on Rocket Lab’s Electron, and Synergy Moon on Interorbital System’s Neptune. All are sharing the nose cone with other payloads on their rockets.

Will Anyone Win the Google Lunar XPRIZE?

Astrobiotics, the top favourite for a long time, have pulled out saying they can’t be ready to launch until 2018. But they are planning a “FedEx service to the Moon” - their Griffin lander will carry other lunar missions to the lunar surface.

In the future we may see tiny rovers image the landing sites.

Artist’s impression of a Google Lunar X-Prize rover at an Apollo landing site. Image Credit: Google Lunar X Prize

(I actually got the image from: Team Indus joins Google Lunar X-Prize finalists, Astrobotic drops out)

That was actually one of the challenges for a bonus prize for the Lunar X prize rather controversially, some think the area immediately around the historic landing sites should be kept pristine and the rovers not permitted to drive over them.

That’s particularly because of the prospect of them landing by accident on top of the flag or some such:

““I’d like to see them demonstrate their ability to do a precision landing someplace else before they try it next to the Apollo 11 site,” Logsdon says. “You wouldn’t have to be very far off to come down on top of the flag or something dramatic like that.” “

Preserving Tranquility

The Lunar Legacy Project say in their Introduction

“Our goal is to preserve the archaeological information and the historic record of Apollo 11. We also hope one day to preserve Tranquility Base for our planet as a World Heritage Site. We need to prepare for the future because in 50 years many travelers may go to the moon. If the site is not protected, what will be left?”

Another group with a similar mission aim is "For All Moonkind".

However none of the finalists plan to take up this part of the challenge as far as I know. So this is not an issue for a while.

Perhaps in the future then we will get Lunar Parks set up, recognized world wide, and rovers and humans will only be able to approach within some set distance of the landing site. The lunar landing sites occupy only a tiny part of the moon’s surface. It’s sometimes called our The Eighth Continent, the second largest after Asia, at 37.9 million square kilometers, it’s larger than Africa, and five times the size of Australia.

So, it's only protecting a very small area, a bit like protecting Stonehenge on Earth. It seems reasonable enough to me.

Though there would need to be some way for scientists to access them if we are going to study the effects of that brief human presence on the Moon, as we discussed in the last section: Trash, rocket exhausts and microbes on the Moon - testing ground for planetary protection measures for a human base . I wonder if that is best done using remote controlled robots for minimal impact? Especially for the biological surveys?

There are no internationally agreed treaties or guidelines yet. But NASA has published a set of guidelines. From: NASA's Recommendations to Space-Faring Entities: How to Protect and Preserve the Historic and Scientific Value of U.S. Government Lunar Artifacts, the requirements include, amongst other things:

  • No overflight. A landed spacecraft mustn't fly over a region of 2 km radius centered on the landing site, or half a kilometer for impact sites like the Ranger probes. That helps avoid risk of accidentally crashing on the sites or of contaminating them with exhaust or debris.
  • The landing ellipse also must be outside of that region. The distance of 2 km places them over the lunar horizon of 1.8 km from the landing site. This 2 km distance is ideal also for dealing with the sandblasting effects of rocks and dust thrown up by the landing. These can have velocities from 300 to 2000 meters per second. The larger ones wouldn't reach the landing site. The smaller ones would fly right over it and miss. There would be some that hit it but they would be small in number.
  • Use natural barriers where possible like hills, crater rims, ridges, terrain slopes to block the spray of the landing spacecraft from the heritage sites.
  • Exclusion zone for rovers etc after landing - they can approach the sites from their landing site 2 km away, but must come no closer than 75 meters for Apollo 11, and 225 meters for Apollo 17. For Apollo 12, 14 - 16 then they recognize that they may need to come closer for scientific investigation, so footprints are not protected, but there's a 3 meter exclusion distance for the descent stage, and 1 meter for the experiments, sampling sites and other artifacts.

For details see the NASA Recommendations.

This is based on the following sections from my Touch Mars? book - be patient, it's around 2000 pages of text in a single web page with many images and videos, so may take a while to load.


This is one of my posts on exploring space in a way that respects the value of science and astrobiology while at the same time valuing humans in space. I hope we can go into a future where both are valued and space settlement as well, all working together.

I think that it will be very sad if we end up with an uneasy conflict in which both science and human exploration suffers. We need to find a "win win" solution here and the Moon is the key to it I think. What we learn on the Moon can help us learn how humans and robots can work together, using the best qualities of each as we explore the solar system.

For more about this vision see my latest article:

And my Touch Mars? book



And I have many other booklets on my kindle bookshelf

My kindle books author's page on amazon


I have written three e-books on this topic of humans in space and planetary protection issues.

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 available on Amazon kindle. It is designed for reading on a computer with embedded videos and links, and I have no plans to attempt a printed version.

As far as I know it's the first book devoted to planetary protection since "When Biospheres Collide".

My other books, which cover human exploration as well as planetary protection, and explore the case for going to the Moon first (for humans), are:


You can get notifications of new posts on my Science 2.0 blog by following the announcements on twitter. You can also 'like' my Facebook page: Science20 Blog Alerts

Any thoughts or comments - do say below.