Pioneer 4, NASA's 1959 fly-by of the moon, was humanity's first visit to another world. Since then, we have explored all of the solar-system's planets, as well as dwarf planets Pluto and Ceres. We have landed on a comet, and dropped a probe through the nitrogen and methane clouds of Titan, Saturn's planet-like moon. Why do we do it? I asked that question to Dr. Daniel Caton, professor of astronomy at Appalachian State University.
Besides for the science and the interest in these planets on their own right, it also allows us to more fully understand our own earth. It's hard to generalize about planets when you're working with a sample of one. In fact, geology has benefited enormously from NASA's probes that have gone to Mars, to Venus, and to the satellites of Saturn and Jupiter because we've seen fascinating geology or planetology going on there. Volcanism on Io, one of the moons of Jupiter, and the murky atmosphere of Titan, that we've landed on and the moon, of course.
We can better understand Earth by understanding other planets' similarities and differences.
For example, there is the Scablands of Washington State, which is an enormous flood event that happened, and there's an equivalent example that we've found on Mars. So we can understand both planets a little bit better when we see that. We can see, maybe, our sad future. For example, Venus is heavily cloud-covered and is in a runaway greenhouse effect. There is severe climate change, natural of course in that case, but it's several hundred degrees in temperature and the atmosphere is heavily CO2, which is what we are emitting from burning fossil fuels.
What about the gas giants of the outer solar system?
Those planets have surprises. They're like 50 centigrade degrees above absolute zero, yet they have weather. They have high speed clouds moving around. They're out at 20 and 30 times the distance the earth is from the sun, so, at the 20 AU, astronomical unit distance of Uranus, it's only one-400th of the energy per square foot of solar radiation. How can you drive weather with that weak of sunlight? Those outer planets do have interesting atmospheric phenomenon that we didn't think would have the solar energy to drive it.
Studying the gas giants' weather systems helps us better model and understand climate and atmosphere on our own planet. What about life? If it was able to get started here, might there also be life elsewhere in our solar system?
There are some moons that do have crystal water ice. And there's ocean below in liquid form that could be warm enough, so to speak, to harbor life. There are hopes that we can go to one of these and have something drill through the ice and then a submersible that goes down to the bottom and look around. Which sounds really not such a good place for life, but we have found life in every place we've looked on Earth. The deepest wells, I mean, bacteria is the major biomass on the planet. The bacteria underground; highly successful in evolution. They've been around forever. And so, hot springs, ice cores in the Antarctic, or in sub-ice oceans, we find life everywhere.
We have rovers actively looking for signs of life on Mars, a planet targeted for near-future human exploration.
I hope we go to Mars. I particularly want a geologist to walk around Mars because the human brain is incredible, and the highly trained geologist brain will look out and see something and go “Whah! What's that?!”, whereas just another rover might just cruise by. And, I think we need that brain there.