Robotic planetary explorers, like the Mars Lander, are making it possible to -- if you will pardon the use of this word -- unearth more about the planets in our solar system. The finding of ice on Mars is a huge discovery. Although it only seems natural that we would make such a discovery, actually seeing the proof is wild. What makes it even more exciting is that life, as we know it, requires water.
When I was a kid, I never thought that we would have the ability to detect planets in other solar systems in my lifetime, and I was a bit of a science geek and a dreamer. With today's powerful telescopes and computers, though, planets in orbit around other stars are being detected by the effects of their pull on their host stars.
Gravity is a two-way street. Stars keep planets in orbit around them with their greater mass, which warps spacetime in such a way that the planets do not fly away. But planets also have a fair amount of mass, which warps spacetime in such a way to cause the host stars to wobble a little bit as the planets orbit. In fact, they wobble enough to be detected from earth, if you have the right instruments. We have those instruments now.
Not only can we detect such planets, we can also now tell if they are within "habitable zones," those orbits around stars where liquid water is possible. If a planet is too close to a star, its water will boil away. If it is too far, it will freeze. Somewhere in between, though, is the Goldilocks Zone, where the orbit is "just right" for liquid water.
Of course, the location of a planet in a habitable orbit does not mean that all the factors necessary for life are present. There are lots of variables that affect the possibility, including the chemical makeup of the planet, and the specifics of its star. That eases the excitement a bit, until we realize that the number of stars in the known universe are estimated at around 50 billion times 100 billion (50,000,000,000 x 100,000,000,000 = 5,000,000,000,000,000,000,000 or 5 times 10 to the 21st power). That is a huge number.
I think there is a very good chance that we'll see evidence of extraterrestrial life within the next 50 years. Looking to that time, I can't help but wonder how that will affect the mind of humanity (Religious fundamentalists will fight the discovery, of course, perhaps violently). For the children born into a world where the presence of life on other planets is a known fact, it will seem as ho-hum as the internet and cell phones are to today's 10-year-olds. The late mythologist Joseph Campbell used to say that we needed a new mythology to guide is in an era when we can see images of the earth from space. I suspect he'd say we'll need a new mythology when we find life elsewhere in the universe, too.
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Here's a story on the Mars Lander finding ice, from about a year ago: http://news.nationalgeographic.com/news/2008/06/080620-ice-mars-photo.html
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