The earliest evidence of a comet entering Earth's atmosphere and exploding has been found. It rained down a shock wave of fire which obliterated every life form in its path, has been found. 

The regions of the U.S. that have doctors and hospitals consolidated into large networks are more likely to have accountable care organizations - medical practice structures that seek to improve medical care and reduce costs - according to a new RAND Corporation paper written to bolster support for the federal Affordable Care Act. 

Consolidation and accelerating growth of large accountable care organizations are a key cost control strategy for Obamacare.

Clouds on Mars look a lot like those on Earth: images of the Martian sky taken by NASA's Opportunity rover depict gauzy, high-altitude wisps, similar to our cirrus clouds.

These clouds likely consist of either carbon dioxide or water-based ice crystals but since we can't sample a Martian cloud yet, it's difficult to know the precise conditions that give rise to them. So researchers have done the next-best thing; they've recreated Mars-like conditions within a three-story-tall cloud chamber in Germany, adjusting the chamber's temperature and relative humidity to match conditions on Mars — essentially forming Martian clouds on Earth.  

With 99% of the Earth's water unused, it might not seem like there could be a water scarcity issue, but water tends to be boom and bust. Many of the poorest regions don't have access to potable water and new estimates by the Potsdam Institute for Climate Impact Research (PIK) if temperatures warm due to climate change.

Bees are more genetically related to ants than they are to social wasps such as yellow jackets and paper wasps, according to a new paper.

 Ants, bees and stinging wasps all belong to the aculeate (stinging) Hymenoptera clade, the insect group in which social behavior is most extensively developed, said senior author and ant specialist Phil Ward, professor of entomology at UC Davis. 

The use of genome sequencing and bioinformatics answers a piece of a long-standing, unanswered evolutionary puzzle. Previously it was thought that ants and bees were distantly related, with ants being closer to certain parasitoid wasps.

Triathletes participate in a grueling endurance sport - in the Olympic version, it means swimming about 1 mile, bicycling 40 miles and then running 6.2 miles. Those in the Ironman version get even more extreme, a 2.4 mile swim, 112 mile bike race and then running a full marathon, 26.2 miles.

Clearly, in both training and competition, they regularly push their bodies beyond the limits most of us can endure. There is no doubt that triathletes are tougher than most people, the mystery is why.