I like to browse around the Astronaut Photography from Earth site occasionally, just to see what the folks overhead have been sending back for us to enjoy. This is one of their latest, taken from the International Space Station. The image tells a story. Look at it for a bit and think about what it tells you. It’s obviously the ocean, with clouds over it, and a sunlight trail across the surface of the water. What is amazing to me is that thin blue line along the limb (edge) of the curved surface of our planet. That’s the extent of the atmosphere. That’s all that’s keeping us from sucking vacuum. Kinda makes you want to protect it, doesn’t it?
My second favorite browsing image from Astronaut Photography today is a mountaintop. Want to guess what and where it is?
Where's today's mystery site? (Click to embiggen.)
It’s a place I’ve visited, has beautiful scenery and spectacular views of both sky and Earth. Click on it to examine the big picture; there’s an important clue right in the center. The answer’s below if you just can’t figure it out!
In all the excitement about planetariums and U.S. politics (and the insanity that is ensuing), poor little Venus Express hasn’t been getting much attention. This is a mission launched by the European Space Agency to study our neighboring planet. It’s loaded with cameras and heat-sensing spectrometers and other instruments so that it can tell us more about that cloud-shrouded world. Well, as it turns out, those instruments can also look at Earth as if it were an alien planet and figure out if it’s habitable.
Yes, indeed folks, we DO KNOW there IS life on Earth. We know it because we’re here. Live evolved here on Earth beginning some 3.8 billion (or perhaps earlier) years ago, spurred by a mix of chemical elements leftover from the formation of the Sun and planets. Some of that “life stuff” was created inside other stars that died long before our solar system existed. It’s a cosmic thang! But, all that’s in the past. Venus Express is looking at Earth now and helping us ask some kind of importan questions, like “What do life signatures look like on a planet?”
Images of Earth (top, from NASA's solar system simulator) and spectra showing the signatures of water and oxygen in our atmosphere, as seen by Venus Express and its VIRTIS system. It took these spectra between April and August 2007. Courtesy ESA/VIRTIS/NAF-IASF/Obs. de Paris-LESIA.
Here on Earth, there’s life ranging from microbes to us monkey-types, and at each level, it leaves clues to its existence. For example, us humans are putting out huge amounts of carbon dioxide, which can be traced in our atmosphere.
Plants, on the other hand, are bright in infrared light, and very soon we’ll have detectors able to discern the signatures of plant chlorophyll on our planet (and others). However, the biggest clues about whether our planet can sustain life are the signatures of oxygen and water in our atmosphere, which Venus Express can see quite nicely, thank you very much.
Okay, you think, big deal! We already knew all that about our planet.
True. But, if you saw those same signatures on another planet, you’d get all excited, wouldn’t you? Such observations would tell you that the planet is capable of sustaining life that relies on water and oxygen. If we’re lucky, and using such instruments as Venus Express has, we might even be able to detect stuff like molecules of chlorophyll.
If you keep the instruments aimed at a planet over a long period of time, as Venus Express is doing with Earth, you can also learn things about the weather systems on that planet (because atmospheric changes over time can be mapped), and maybe even something about oceans and glaciers, which have their own unique ways of interacting with the atmosphere.
The amazing thing about the Venus Express observations is that, from its point of view, Earth is less than a pixel wide. It appears as a single dot. Which is a LOT like how planets around other stars look to us right now. Yet, it was able to get detailed spectra of Earth’s atmosphere and figure out that the conditions for life exist here.
Since we’re on the verge of finding Earth-like planets, astronomers using techniques and instruments similar to those of Venus Express will very likely be able to track down any life-bearing (or life-bearing-capable) worlds. The one thing we won’t be able to tell about that distant life is whether it’s intelligent or not. That will have to wait until we intercept alien signals and can figure out what they’re saying to each other (and the cosmos). (Let’s hope we don’t get the equivalent of THEIR political debates being broadcast to the neighbors — I’d hate to find out that the Greeblethorax Old Party on 55 Cancri IV also doesn’t like planetariums!)
