appearance of a lightly-shaded patch that has all the hallmarks of being caused by water bubbling up from under the Martian surface and running down the 30 degree slope
While there may be other explanations, the pictures are stunning. If this is water, I think we have to start to come to grips with the high probability that life will be found on Mars. In other words, not only might life have existed there in the past, but I think it is reasonably likely that there is life there now. Now before you get all hoity toity on me - I am not talking about little green men here. But possibly little green microbes. Or little pale microbes that use chemical energy to fix carbon and grow. Such microbes are of course all over earth, in the deep sea, in hot springs, in tidal flats, in animal guts. The real questions (again, if this is really water) the become:
- could life have evolved separately on Mars?
- could microbial life from Earth have seeded Mars?
As for question 2 - I think life easily could have been transported between the two planets. All you really need is for a meteorite or comet collision with Earth to blast some moderately sized pieces of material off of Earth into space. Microbes in such material could have survived for some period of time on such pieces in space (remember, many microbes do not need oxygen, and can survive incredibyl harsh conditions on Earth). Imagine if a big piece of Earth was knocked off the planet - microbes in the center of such a piece would be protected from some of the radiation and other stresses of space. And you just need one of these pieces to end up on Mars for the cross-seeding event to occur. Of sure, there are a series of assumptions here and a multiplication of low probability events. But we can make up for low probability by multiplying by 3.5 or so billion years - the amount of time that life has existed on Earth.
So this raises one final issue for me. The person with the greatest job title in the world - John Rummel, better get moving. He is the "Planetary Protection Officer" for NASA - charged with protecting other planets from Earth and Earth from other planets. One of his main jobs is to think about how to make sure the Martian missions do not bring microbes with them to Mars so that if microbes are found there we can assume they are from Mars not earth. Unfortunately in my google searches about this it seems Dr. Rummel has been promoted within NASA and I cannot figure out who took over his old job. Does that alas mean we are temporarily without a planetary protection officer? I hope not.
Whether it turns out life exists or existed on Mars or not, the finding of apparently flowing water on the surface is wildly exciting and proof to me that Mars missions are critical to our understanding of the world around us.