Category Archives: exoplanets

Earth, exoplanets, planets, Venus Express

But is it Intelligent Life?

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Venus Express Looks for Earth Life

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) and spectra showing the signatures of water and oxygen in our atmosphere, as seen by Venus Express
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!)

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astronomy news, astronomy research, exoplanets, exploration

Earth As An Exoplanet

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How We Might Look to the Neighbors*

*If They Had a Good Set of Instruments and a Clear View

RGB comp of deconvoluted frames of Earth and Moon

Astronomers are enjoying an unprecedented time of planetary discovery. As of May, 2008, here have been 293 planets found around other stars. That number will change, and in fact, it already has, and it’s only the 2nd of June.

These planetary discoveries have the potential to teach us a lot about how and where planets are scattered around the galaxy, and perhaps other galaxies as well. But, here’s what’s also cool–at least one mission out there, the former Deep Impact Mission to a comet–is now spending its time looking for other planets. And, once in a while it turns its eye back to Earth to look at our home planet as if it were an exoplanet. It’s not the first time a spacecraft has looked at Earth, but it is the first time one has done it with an array of instruments tuned to study the light from our planet (and others) in high detail.

The image here was taken by the spacecraft on May 29, 2008, and shows the Moon in its orbit around Earth. It shows our planet from the spacecraft-eye view; if a nearby civilization had a similar spacecraft and looked at us with it, they’d likely see a bright spot (if they could manage to separate us out from the glare of the Sun).  If they had a REALLY good instrument, they’d probably notice that our brightness would dim occasionally and periodically, almost like something is passing in front of us.

The idea behind looking at our home world as if it was an alien planet is so that we can use what we find to compare it to other planets we might find. If we can understand how we look to the neighbors (i.e. our color, atmospheric properties, distribution of continents and oceans) then it will help us recognize similar properties when we see them on other planets.

At the summer meeting of the American Astronomical Society, being held this week in Saint Louis, astronomers working on the EPOXI mission (using the Deep Impact craft) talked about their work. They said that later this summer they’ll release a time-lapse movie of the Moon transiting Earth. As it passes between Earth and the point of view of the spacecraft, it will cover up places like the deserts of North African, which reflect a lot of light.

To a distant observer, this kind of transit would show up as a dimming of the planet (which would actually appear pretty bright since its surface areas and clouds reflect light). This well-known transit effect is also how astronomers can “see” or actually infer the existence of larger planets around stars. The light blockage is what what helps them detect the existence of a planet. So, the story of planetary discovery keeps on ticking, like that well-known battery-operated bunny rabbit. There are, in fact, more results from the meeting that I’ll write about in another post. But for now, enjoy the pretty sight of Earth from “alien eyes” and think about what it will be like when we find another Earth out there.