Computer Science – Sound
Scientific paper
Jan 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003xmm..pres...85.&link_type=abstract
XMM Press Release SNR 1-2003
Computer Science
Sound
Scientific paper
Ozone in a planet's spectrum may indicate the presence of life hi-res
Size hi-res: 673 kb Credits: ESA 2001. Illustration by Medialab
Ozone in a planet's spectrum may indicate the presence of life Darwin will most probably look for the spectral signature of ozone, which is unlikely to exist in any quantity for any length of time in the atmosphere of a planet that is not home to life. The background image is a view of Earth seen by the Apollo 17 crew as they traveled toward the Moon. The white patch at the bottom is Antarctica. Unobscured by clouds, Africa and the Arabian Peninsula are visible at the top of this image. The large island off the coast of Africa is the Malagasy Republic.
Looking for Earth-like planets hi-res
Size hi-res: 2106 Kb Credits: ESA 2002. Illustration by Medialab
Looking for Earth-like planets Darwin has six telescopes that analyse the atmospheres of Earth-like planets
Darwin's flotilla hi-res
Size hi-res: 902 Kb Credits: ESA 2002. Illustration by Medialab
Darwin's flotilla Darwin's six telescopes, a central view-combining spacecraft, and communication satellite (shown bottom left)
Our radio and television broadcasts have been leaking into space since the 1930s, when the first powerful emitters were constructed. However, you can do things the other way around as well. The Search for Extraterrestrial Intelligence (SETI) has used radio telescopes to listen to the cosmos for similar signals.
Nowadays, astrobiologists are pinpointing more subtle signs that all life, not just intelligent life, might radiate into space. They call these telltale signatures 'biomarkers'. When ESA's Darwin mission begins sending back data in the next decade, biomarkers will help indicate whether neighbouring planets are inhabited.
If we only used radio waves as markers of life, this would exclude all forms of life that have not yet developed the means to emit radio waves. Life has been around for thousands of millions of years, but human beings have used radio waves for less than a century. Malcolm Fridlund, Project Scientist for ESA's Darwin mission says, "If other planets follow the Earth's pattern, it is much more likely that they will be inhabited by dinosaurs or even bacteria than by something that can count."
In the 1970s, the British scientist James Lovelock pointed out that, just by breathing, life affects the composition of the Earth's atmosphere. He suggested looking for similar effects as a way to search with telescopes for life on other planets. You can study the composition of an atmosphere by splitting a planet's light into a rainbow of colours. This 'spectrum' will contain dark lines made by various chemicals in the planet's atmosphere.
Darwin's strategy is to look for oxygen because oxygen is used by some life forms and produced as waste by others. Scientists believe that without life, all free oxygen in a planet's atmosphere would disappear within just four million years, because it reacts so easily with other chemicals. "The best estimates suggest that Darwin will be able to detect the build-up of oxygen caused within a few hundred million years of life's origin," says Fridlund.
Although Darwin will not detect oxygen directly, it will 'see' ozone, a form of oxygen. It will also see carbon dioxide, water, and, in certain cases, methane. Fridlund says, "The general consensus is that if we find ozone, liquid water, and carbon dioxide simultaneously, it will be a very strong indicator of life's presence."
The work will not stop once Darwin completes its survey of the nearest several thousand star-planet systems. Once it finds a living planet, the race will be on to understand the nature of its life forms. That means searching for more specific biomarkers. In future space missions, for example, scientists may use chlorophyll as a biomarker. This molecule allows plants and certain bacteria to use light as an energy source. "Finding the next generation of biomarkers is a very active field of research at the moment," says Fridlund.
He can see a future in which space telescopes look for intelligent civilisations by searching for industrial pollution in a planet's atmosphere. This may sound like science fiction but for now, oxygen, carbon dioxide, and water will be good enough as indicators of life.
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