Hubble camera spots traces of life-forming gas
http://www.latimes.com/news/science/la-sci-methane20mar20,1,46130.story
By John Johnson Jr., Los Angeles Times Staff Writer
March 20, 2008
Scientists detected traces of the first organic molecules in the
atmosphere of a planet orbiting a far-off star, a development that may
lead to the ability to uncover the signatures of life on worlds
outside our solar system.
Using the Hubble Space Telescope's infrared camera, a team led by
researchers at the Jet Propulsion Laboratory in La Ca=F1ada Flintridge
found methane and water in the atmosphere of a planet orbiting a star
roughly 63 light-years away.
The Jupiter-size planet orbits far too close to its parent star in the
constellation Vulpecula for life as we understand it, the team
re****ted Wednesday in the journal Nature.
But Mark Swain, an exoplanet specialist who led the research,
described the technique the scientists had used as "a crucial stepping
stone to eventually characterizing pre-biotic molecules on planets
where life could exist."
One expert praised the work but said she would like to see more proof.
"This is really pu****ng the telescope to its limits," said Sarah
Seager, a planetary scientist at MIT. "I'm cautiously optimistic" that
the finding is real.
Water and methane are not necessarily the building blocks of life on
giant planets such as this one, HD 189733b, Seager said. Their gravity
is so great that they retain all of the original chemicals and
compounds they started with.
The detection of methane, composed of four atoms of hydrogen and one
of carbon, on a smaller planet would be a better indication of
biological processes. Whatever natural methane they had at their
formation would have long since escaped to space. An indication of a
lot of methane would mean that something is continuing to feed the
atmosphere with it. On Earth, many life forms give off methane.
The gas can also be a precursor to life.
"Under the right conditions, it can form amino acids, which are the
building blocks of life," Swain said.
Of the 200 or so exoplanets discovered so far, most are like grown
children who refuse to move out, sticking close to their parent stars.
This planet has a two-day orbit, which puts it so close to its star
that it would quickly cook any life forms before they got started.
Finding these big, skirt-hugging planets is easier than finding their
more independent siblings because they are so close to their parents
that they cause a tiny wobble in the stars' movements. HD 189733b was
found by measuring the slight dimming of the star's light caused by
the planet crossing in front of it. The signature for methane was
found in a spectroscope analysis of the light.
Scientists are pinning their hopes of finding Earth-like exoplanets,
those smaller and farther out, on the next generation of telescopes,
specifically the James Webb Space Telescope. Scheduled for launch in
2013, it will have a 21-foot-diameter mirror, allowing it to gather
six times as much light as Hubble.
The James Webb will orbit 1 million miles from Earth, much farther
than Hubble, allowing the infrared instruments to screen out the heat
and light reflected from the planet.
"I'm really excited about five years from now," said Seager, when the
Webb telescope will be able to pinpoint "super Earths." These are
planets bigger than Earth but located in the so-called Goldilocks zone
around stars where it's neither too cold nor too hot.
john.johnson@[EMAIL PROTECTED]
|
