NASA's Mars Science Laboratory, named Curiosity, had some really big news this week. They found that Mars was once a place where life could have arisen. Wait a second, that's a strange sentence. Did they find life? Sadly, no. Did they find fossils? Again, no dinosaur bones or ancient camel humps were found (like those recently found in the arctic.) Did they find puddles of water and moss and plants and bacteria? Well, sorry, no again. OK, so what did they find? Basically, what they found was a well-set dinner table for some very picky dinner guests. Curiosity was at a location called Yellowknife Bay, where it's been scooping up Martian soil, drilling into rocks, sifting it with a sifter, and looking at it really closely. If you want to do the same things at home that Curiosity is doing on Mars, you can start with the following: get a magnifying glass and go out to your yard. Look for a patch of soil that your fingers can easily pull up. Take a scoop with your fingers and look at the soil with the magnifying glass. What do you see? Well, you should see seeds and roots, maybe some little bugs, but you should definitely see soil. Now, on Mars, there are no seeds or root or bugs, so let's push those out of our hand, and look just at the soil and rocks. A good front-yard soil should be black or maybe, if you grew up where I did in Minnesota, it can be so rich with minerals that it's blue. OK, now that black soil comes from a mix of dead and decomposed plants and bugs, so let's brush away the black soil. Now what are we left with? Maybe we have some little pebbles and some glittering rocky dust. Now then, take this to a chemist at a laboratory, and tell him or her how you did this and ask to look with a really good microscope. We might find that on these little pebbles that there are some microbes and bacteria that live on the rock and eat the rock as food. There will be some kinds of rock that don't yet have such bacteria, and some which once did, but the bacteria have moved on after eating their fill. These are the kinds of rocks that Curiosity has found. They found rocks that, if we took some normal-looking, rock-eating bacteria on Earth, put them on the rock, and flooded the rock with a lot of water, the bacteria would be happy and grow and eat the rock.
This means that Curiosity found a well-set dinner table. Combine this with what was found a couple of months ago that at Gale Crater there are rocks that were clearly smoothed by running water, and you have a place on Mars that was suitable for life to arise. In fact, Curiosity's team has determined that the water that was once in Gale Crater would have even been drinkable by you and me!
Wow! Does that mean that life is there now and that life could be there now? Probably not. Mars is a tough place, and besides, Curiosity is not built to look for that. What we can only say is that about 3 billion years ago on Mars, in Gale Crater, there was a lot of water, and that the rocks that were there and the chemicals in those rocks could have supported some of the same simple forms of life that we have here on Earth. Now, today it's too dry and too cold to support surface life, even of the simplest kind. We still don't know whether life actually arose on Mars, but we are now certain that Mars was a bacteria's favorite restaurant. The table was set, the waiters were waiting, the doors were open, and the music was playing. Did anyone walk in and nibble on those tasty non-oxidized rocks and sulfates and sulfides? We don't know. But at least we now know it could have happened.
Here are a few helpful links I found...
- Full NASA article
- On Earth we have some places that look a lot like Yellowknife Bay, with the same rocks and the same dry environment.
- Here's what a fossilized ancient streambed looks like on Mars
- Compare the water-rolled rocks on Earth to Mars