Tuesday, April 22, 2008

Earth Day 2008

Earth as seen from Mars
Image Credit: NASA/JPL-Caltech/University of Arizona

Today is Earth Day! But I promise not to fill this space with discussion of climate change and sustainability and the like, as there is plenty of that discussion out there already.

However, I would like to note how crucial studies of the Earth are to astronomy research, as looking inward gives us a reference point for interpreting what we see when we look outward.

Planetary astronomers get the most direct help from studies of the Earth. Other planets and moons have volcanoes, fault lines, atmospheres, and weather. It is not hard to imagine how understanding lava flows on Earth may help us to understand the history of Martian volcanoes, or how knowledge of cloud formation on Earth can help us understand why Venus is shrouded in clouds, or even the development and structure of clouds on Jupiter.

In the next decade, we will most likely discover Earth-sized planets around other stars. And as we develop more and more sophisticated technology capable of analyzing light from those planets, we will likely begin to detect other atmospheres. How reliably can we interpret those findings from far away? Studies of the Earth from afar (like the above picture of Earth and our Moon taken from Mars late last year) can tell us what we can and cannot detect from far away.

Finally, as we begin to look for life on other planets, we need to know how to look for life. Most importantly, are there any unambiguous signs of life that we'd be able to see from hundreds of light-years away? Our atmosphere has concoctions of molecules, like methane, oxygen and ozone, that we don't think other planets can have without life producing them. But maybe other non-biological processes that we haven't thought of could be at work. Do we need to look for signs of chlorophyll? Would alien plants use chlorophyll? What if we see some strange molecule that we don't have on Earth. Could we identify it and discover if it is a marker of life?

These are all important questions, and while studying our own planet may not provide us with unambiguous answers, maybe we can get some guidelines toward solving these problems. And, in the meantime, we'll continue to learn more about our home planet, our relation with it, and how we should best maintain it.

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