Category Archives: planets

But is it Intelligent Life?

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!)

****************

(Have you registered to vote?)

A Lesson in Earth Science

And Climate Change

Sometimes you can’t keep ahead of the news. Especially in science.  As I was working on the climate change exhibits for California Academy of Sciences earlier this year, I’d keep tabs on research and discoveries in Earth sciences, particularly Earth’s atmosphere and oceans. And, as fast as I’d write up something from peer-reviewed science, there’d be more information and discoveries coming in.  Which is great, but when it comes to climate change, it seems like it might be chronicling drastic change that we neither need nor want.  But, that’s the nature of science research — it reports on what’s happening and tries to find out why it’s happening.If we’re smart, we heed what we see and take action.

Tomorrow there’s a peer-reviewed science paper coming out that I wish had come out earlier, since it would make a striking addition to the exhibits. It states that as Earth’s oceans absorb more carbon dioxide generated by human consumption of fossil fuels and other activities (which warms up oceans and causes them to become more acidic), sounds will travel farther underwater. What’s the big deal, you might ask.  Well, noisier oceans affect marine mammal, for one thing. And, there are likely other effects that reverberate throughout the ocean environment.

Image credit: (c) 2008 MBARI (Base image courtesy of David Fierstein). This illustration shows how increasing carbon dioxide in the atmosphere leads to an increase in the acidity of seawater, which in turn allows sounds (such as whale calls) to travel farther underwater.
Image credit: © 2008 MBARI (Base image courtesy of David Fierstein). This illustration shows how increasing carbon dioxide in the atmosphere leads to an increase in the acidity of seawater, which in turn allows sounds (such as whale calls) to travel farther underwater.

This projected impact on ocean sound is the result of calculations by Keith Hester and his colleagues at the Monterey Bay Aquarium Research Institute (MBARI) in Moss Landing, Calif. Their paper is coming out in tomorrow’s (October 1, 2008) issue of  Geophysical Research Letters, a journal of the American Geophysical Union (AGU).

So, what does it mean? Ocean chemists know that as seawater chemistry changes, its ability to absorb sound changes. As sound moves through seawater, it causes groups of atoms to vibrate, absorbing sounds at specific frequencies. This involves a variety of chemical interactions that are not completely understood.

The overall effect is strongly controlled by the acidity of the seawater. The bottom line is this: the more acidic the seawater, the less low- and mid-frequency sound it absorbs.

As the oceans become more acidic, sounds will travel farther underwater and the level of underwater noise will rise. This change in chemistry will have the greatest effect on sounds below about 3,000 cycles per second (two and one half octaves above “middle C” on a piano).

This range of sound includes many of the underwater noises generated by industrial and military activity, as well as by boats and ships. Such human-generated underwater noise has increased dramatically over the last 50 years, as human activities in the ocean have increased. For marine mammals that also use this range of sounds to communicate, it’s like having your neighborhood go from one of relative quiet to one where the neighbors are blasting their stereos and revving their engines all the time.

The MBARI researchers say that sound already may be traveling 10 percent farther in the oceans than it did a few hundred years ago. However, they predict that by the year 2050, under conservative projections of ocean acidification, sounds could travel as much as 70 percent farther in some ocean areas (particularly in the Atlantic Ocean). This could dramatically improve the ability of marine mammals to communicate over long distances, but, on the down side, it could also increase the amount of background noise that they have to live with.

There are no long-term records of sound absorption over large ocean areas. However, the researchers cite a study off the coast of California which showed an increase in ocean noise between 1960 and 2000 that was not directly attributable to known factors such as ocean winds or ships.

Hester’s research shows how human activities are affecting the Earth in far-reaching and unexpected ways. As the researchers put it in their paper, “The waters in the upper ocean are now undergoing an extraordinary transition in their fundamental chemical state at a rate not seen on Earth for millions of years, and the effects are being felt not only in biological impacts but also on basic geophysical properties, including ocean acoustics.”

*********