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The Sciences

Mars’ Past Habitability Is Even More Likely

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Big news today from the Martian front. New data from everyone’s favorite car-sized roving robot, Curiosity, has come out, with implications for potential life on the Red Planet. At a press conference today at the American Geophysical Union’s fall meeting in San Francisco, and in a bundle of six Science papers

, scientists announced the extreme likelihood of an ancient lake near Curiosity’s landing site that was habitable for certain microbes, as well as greater details about the geological history of the landing site and the amount of harmful radiation that the rover’s been exposed to. You may be forgiven for thinking this sounds a bit familiar.

Mars’ Microbes

Let’s start with what seems like the biggest news, from the most epically titled paper of the bunch: "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars

." (Fluvio-lacustrine, just on the off chance you’re unfamiliar with the term, is a geological term meaning “produced by lakes and rivers.

”) Yellowknife Bay is the specific area under scrutiny within Gale Crater, the 154-kilometer-diamater area where Curiosity landed and wanders. By analyzing the environment with its lasers and drills and other fancy instruments, the rover found data suggesting the site was once habitable, home to flowing water with neutral pH, low salinity and various important elements for life like carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorous. This means microbes known as chemolithoautotrophs

, known to thrive in Earth’s caves and hydrothermal vents on a diet of chemicals, could have almost certainly lived in that ancient Martian lake. Great news, sure, but it was a bit more impressive the first time

. We’ve known about that particular ancient lake and its likely habitability for almost a year now. These new findings solidify the scientists’ suspicions of habitability and do provide a timeframe for the lake, suggesting it existed in habitable form for tens or hundreds of thousands of years. Science is often iterative, and builds slowly upon itself — these findings are definitely important to other scientists and anyone extremely interested in Mars’ past habitability. But it’s also important to keep perspective on findings like this, too.

Totally RAD Findings

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A graph compares radiation dosage on Mars with various earthbound sources. Of the other five papers in the bundle, three deal with the minutiae of Curiosity’s geologic findings, one deals with a new method of dating the rocks on and just beneath Mars’ surface, and the final one

reports on the radiation the rover’s received on the surface. This last one might also seem like another rehash of old news

, but it is worth exploring briefly. It’s easy to forget, but among Earth’s finer qualities is its ability to shield us from the hazardous radiation rampant in space, mostly from galactic cosmic rays and solar energetic particles. The journey to Mars would prove somewhat dangerous for humans on board any but the most heavily shielded vessel, and landing on Mars would only offer a minor improvement. Curiosity’s Radiation Assessment Detector, after 300-odd days on the Red Planet, measured the total average radiation rate to be about 0.21 microgray per day (mGy/day), only about half the 0.48 mGy/day it picked up during the journey in space. (Measuring radiation is weird, but see here

and here

for pointers.) In total, the scientists now estimate the surface rate at 76 mGy/yr. That’s pretty high, but not intolerable, for humans and other life. Knowing this will help us plan for possible future Mars exploration (and put further bounds on the unlikely scenario of Martian life currently existing). http://www.youtube.com/watch?v=X-iqwAt2Qmk&feature=youtu.be

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