Although I’ve written about this in previous years, the new data from Curiosity now show much stronger evidence than before that Mars once had large lakes or perhaps even an ocean.
Layer upon layer of sedimentary rock clearly shows that Mars had more than just a bit of water on its surface in the past. In fact, it once had a large body of water that lasted many millions of years.
That is long enough to imagine that life (in the form of microorganisms) might have taken hold on Mars before going extinct.
There still is no direct evidence of microbial life ever being present on Mars, but the environment there billions of years ago appears to have been suitable for sustaining life. Before Curiosity, this idea was speculative. Now, the evidence is nearly undeniable.
Even though Curiosity still has a lot of work to do, we can start thinking about the next step: a dedicated mission to look for possible fossil evidence of long-ago microbial life on Mars. Although Curiosity can detect organic material, its primary mission was to look for geological evidence of a habitat that could sustain life. This it has done well. But finding evidence of primordial life is another matter.
If you think about fossils on Earth, usually what comes to mind is the imprint of bones left in a rock after a dead animal decomposed and then was covered by sediment. Over many years — and more layers of sediment — the dirt becomes rock and the bones leave a telltale impression.
The problem on Mars is, of course, that microbial life has no bones. The only evidence that would remain is organic molecules that are typically made by living things. Over long periods of time, even these organic compounds would undergo chemical reactions, leaving little trace of their existence.
Searching for evidence of organics is further complicated because simple organic molecules are found in meteorites, which constantly bombard Mars (and other planets). What we really need to find are complex organic molecules, and if these exist, they probably are locked deep underground, where Curiosity can’t go.
Curiosity has drilled an inch or so into rocks and found organic compounds. Although this is promising, there still is no “smoking gun” discovery of organics unique to Mars.
This all leads to the suggestion that a manned mission to Mars is necessary. Advocates of this mission say that only humans have the flexibility to fully investigate Martian rocks for evidence of life.
I might agree with this in principle, but I think it’s much better to bring rocks back to Earth rather than transport humans to Mars. Sending humans to Mars would contaminate the landscape. If you’re trying to find a tiny grain of sand on a pristine floor, you don’t walk all over the floor with dirty shoes.
A human mission would spread organic materials into the Martian environment, while robots such as Curiosity are relatively clean. Of course, even robots need to get to Mars, and this would be easier with the new rockets being built by NASA.
The Space Launch System, which would be more powerful than the older Delta IV rocket, will be tested in 2017. This new rocket makes possible a mission to bring Mars rocks back to Earth for better analysis.
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