Published in The Patriot Ledger October 27, 2012:
It has now been forty years since we last landed men on the moon, but there’s excitement in space again. NASA’s rover Curiosity recently discovered an ancient streambed on Mars – an array of rounded rocks that clearly had been shaped by tumbling action in flowing water. This must have been an important discovery, because it received a few seconds of coverage on ABC News and other news outlets, almost as much as the day’s campaign news.
We associate water with life, and the possibility of life on Mars has long been of interest to us earthlings, especially any of us who read H.G. Wells’s “War of the Worlds.” Curiosity is only the latest of many space probes NASA has sent to Mars. Back in the 1960s, in the early days of the space race, we got our first close-up pictures of the Mars surface with fly-by probes, but there was no evidence of the advanced civilization that many had imagined there.
Starting in the 1970s, we put ships into orbit around Mars, and the orbiters have produced more and more detailed photos of the entire surface of the planet. We still have found no evidence of “little green men,” but we have discovered a very complex and fascinating landscape, including extinct volcanoes many times higher than Everest and a giant canyon that dwarfs our Grand Canyon. And we found much evidence of past water flow in the form of dry riverbeds and of gullies on the walls of impact craters.
We landed two rovers, Spirit and Opportunity, in 2004, and during their years of roving miles across Mars, they found layered rock believed to be sedimentary rock deposited on the floor of ancient lakes. With their geology instruments, they identified several specific minerals that we know to be formed from water. They made lots of interesting discoveries, but they didn’t find what Curiosity found in its first few weeks – an ancient streambed.
That streambed probably hasn’t had flowing water for a long, long time – perhaps a billion years or more. But if Mars had flowing water then, it must have been warmer, and had more of an atmosphere, than it does now. And that was about when we believe microbial life first began on early Earth. So scientists are searching for evidence of past or present microbial life on Mars. The discovery that life independently evolved on Mars would be sensational news indeed.
Curiosity traveled several hundred million miles through space to land successfully in a target zone only a few miles wide, an amazing technical achievement. It is much larger, and carries a lot more advanced scientific equipment, than the earlier Mars rovers. In the coming months, it will be looking for evidence of the past habitability of Mars, further evidence of water and perhaps evidence of organic compounds, the basic building blocks of life.
In its youth a billion or so years ago, Mars was apparently much more like Earth than it is today. Today Mars is cold and dry, and what little atmosphere it has is mostly carbon dioxide. Not the most welcoming of environments. But it remains the most Earth-like of the other planets, and the most likely target for manned exploration – and for colonization. (The Earth is getting crowded!) The discoveries of Curiosity and the earlier probes are preparing the way. Perhaps it will not be until we land astronauts on Mars that we finally find firm evidence of early life on Mars. Or perhaps the early settlers will eventually conclude that they themselves are the first life on Mars.