SCIENTISTS SEEK SCENT OF LIFE IN METHANE AT MARS
By Leonard David
24 August 2004
Sniffing out any whiff of biology on Mars has become a scientific battle of the bands—spectral bands that is. The purported detection of methane in the martian atmosphere by Mars Express, the European Space Agency (ESA) probe now orbiting the red planet, has sparked measurable debate.
ESA announced late last March that the Mars Express Planetary Fourier Spectrometer (PFS) had observed methane. That instrument is built to detect the presence of particular molecules by analyzing their "spectral fingerprints"—the specific way each molecule absorbs the sunlight it receives.
While the amount of methane seen by the PFS is very small—about 10 parts in a thousand million—the implications of the detection are large. Perhaps Mars isn’t a planet waiting to exhale, but one that is a thriving world of panting microbes. According to ESA experts, methane, unless it is continuously produced by a source, only survives in the martian atmosphere for a few hundreds of years because it quickly oxidizes to form water and carbon dioxide—both present in the martian atmosphere. So what’s refilling the atmosphere with methane?
Read the full article at http://www.space.com/scienceastronomy/mars_methane_040824.html.
BRITISH SCIENTIST ASKS NASA FOR HELPING HAND TO MARS
From Agence France-Presse and SpaceDaily
24 August 2004
The British scientist who masterminded the ill-fated Beagle 2 probe, which vanished while attempting to land on Mars, said Tuesday he wanted to try again and has asked NASA for a ride to the Red Planet. Professor Colin Pillinger said he had written to the US space agency asking whether room might be found for a successor to Beagle on a much larger US mission to Mars due to depart in 2009. Speaking at a press conference to unveil an investigation into what went wrong with Beagle 2, which vanished shortly before it landed on Mars on Christmas Day last year, Pillinger said his team was "looking at the future".
NASA successfully landed a pair of probes on Mars around the same time as Beagle was lost, and is now planning to send a Mars Science Laboratory, a much larger device designed to roam the planet for years.
"I sent a letter to NASA saying, would you be interested in taking the Beagle 2 lander as a stand-alone package on a rover?" Pillinger said. "We're looking at any opportunity and every opportunity."
Read the full article at http://www.spacedaily.com/2004/040824133031.f4j7pkc6.html.
PERIODIC DIMMING OF BRIGHT STARLIGHT REVEALS DISTANT PLANET
National Center for Atmospheric Research release
24 August 2004
Scientists have made their first direct discovery of a planet orbiting a bright star using a network of small telescopes and the "transit method" of detection. A periodic dimming of light from a bright star 500 light years away revealed the planet's presence. The star's intense light will allow scientists to explore the chemical makeup of the planet's atmosphere in future observations. A paper on the recent discovery will appear in The Astrophysical Journal Letters.
This is the first extrasolar planet discovery made by a dedicated survey of many thousands of relatively bright stars in large regions of the sky. It is also the first using the Trans-Atlantic Exoplanet Survey (TrES, pronounced "trace"), a network of small, relatively inexpensive telescopes designed to look specifically for planets orbiting bright stars. The telescopes make use of the transit technique, in which scientists analyze the shadow cast by a planet as it passes between its star and Earth.
This artist's rendition of TrES-1 shows it circled by small asteroids as it orbits its bright star. Illustration by David A. Aguilar, Harvard-Smithsonian Center for Astrophysics.
The discovery team includes scientists from the Astrophysical Institute of the Canaries (IAC), National Center for Atmospheric Research (NCAR), Harvard-Smithsonian Center for Astrophysics (CfA), Lowell Observatory, and California Institute of Technology. A team of scientists led by Timothy Brown (NCAR), David Charbonneau (CfA), and Edward Dunham (Lowell Observatory) developed the TrES network. Brown built the optical system of the telescope used in the discovery and located on Tenerife in the Canary Islands. A graduate student of Brown's, Roi Alonso Sobrino, of the IAC, discovered the planet, called TrES-1, after three years of persistent planet hunting.
"The fact that we can learn anything at all about a planet 500 light years away is astonishing," says Brown.
The network's other two telescopes are located at the Lowell Observatory in Arizona and at Mt. Palomar, California.
"It's almost paradoxical that, with the transit method, small telescopes are more efficient than the largest ones, in a time when astronomers are planning 100-meter telescopes," says Alonso.
Of the approximately 12,000 stars examined by the TrES survey, Alonso identified 16 possible candidates for planet transits.
"The TrES survey gave us our initial lineup of suspects. Then, we made follow-up observations to eliminate the imposters," says co-author Alessandro Sozzetti (CfA/University of Pittsburgh).
After compiling the list of candidates in late April, the researchers used telescopes at CfA's Whipple Observatory in Arizona and Oak Ridge Observatory in Massachusetts to obtain additional photometric (brightness) observations, as well as spectroscopic observations that eliminated eclipsing binary stars. In a matter of two month's time, the team had zeroed in on the most promising candidate. High-resolution spectroscopic observations by Guillermo Torres (CfA) and Sozzetti using the 10-meter-diameter Keck I telescope in Hawaii clinched the case.
"Without this follow-up work the photometric [brightness] surveys can't tell which of their candidates are actually planets. The proof of the pudding is a spectroscopic orbit [using the Doppler method] for the parent star. That's why the Keck observations of this star were so important in proving that we had found a true planetary system," says co-author David Latham (CfA).
More than 120 planets have been found by the Doppler method, which detects the gravitational pull of the planet on its star, but only gigantic planets can be "seen" this way. Moreover, the Doppler method gives indirect information about a planet. In 1999, the transit method was first used successfully to confirm the existence of a planet that had been discovered through its gravitational effect. Only now has the transit method resulted in a discovery involving a Jupiter-size planet circling a bright star. The success of the transit method opens the possibility of directly determining key information about the planet, such as its mass and radius (size), and its atmospheric components.
Next step: exploring the TrES-1 atmosphere
Scientists study an extrasolar planet's atmosphere by using a technique called spectroscopy. As starlight passes through the planetary atmosphere, light at some wavelengths disappears. This occurs as elements and compounds in the atmosphere, such as methane and carbon monoxide, absorb light at specific wavelengths. By observing which wavelengths are absorbed, Brown and colleagues will learn which elements are present in TrES-1's atmosphere. The scientists plan to search for water vapor first, since it can give clues about other chemical components.
"All that we have to work with is the light that comes from the star," says Brown. "It's much harder to learn anything when the stars are faint."
Three planets have been found with the transit method using large telescopes aimed at faint stars. However, the starlight is too dim to examine the planetary atmospheres.
Brown's research is funded by the National Science Foundation, NCAR's primary sponsor, and by NASA.
Read the original news release at http://www.ucar.edu/news/releases/2004/planet.shtml.
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European Southern Observatory release
25 August 2004
A European team of astronomers  has discovered the lightest known planet orbiting a star other than the sun (an "exoplanet"). The new exoplanet orbits the bright star mu Arae located in the southern constellation of the Altar. It is the second planet discovered around this star and completes a full revolution in 9.5 days. With a mass of only 14 times the mass of the Earth, the new planet lies at the threshold of the largest possible rocky planets, making it a possible super Earth-like object. Uranus, the smallest of the giant planets of the Solar System has a similar mass. However Uranus and the new exoplanet differ so much by their distance from the host star that their formation and structure are likely to be very different.
Montage of the HARPS spectrograph and the 3.6m telescope at La Silla. The upper left shows the dome of the telescope, while the upper right illustrates the telescope itself. The HARPS spectrograph is shown in the lower image during laboratory tests. The vacuum tank is open so that some of the high-precision components inside can be seen.
This discovery was made possible by the unprecedented accuracy of the HARPS spectrograph on ESO's 3.6-m telescope at La Silla, which allows radial velocities to be measured with a precision better than 1 m/s. It is another clear demonstration of the European leadership in the field of exoplanet research.
Since the first detection in 1995 of a planet around the star 51 Peg by Michel Mayor and Didier Queloz from the Geneva Observatory (Switzerland), astronomers have learned that our Solar System is not unique, as more than 120 giant planets orbiting other stars were discovered mostly by radial-velocity surveys. This fundamental observational method is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an (unseen) exoplanet as it orbits the star. The evaluation of the measured velocity variations allows to deduce the planet's orbit, in particular the period and the distance from the star, as well as a minimum mass .
The continued quest for exoplanets requires better and better instrumentation. In this context, ESO undoubtedly took the leadership with the new HARPS spectrograph (High Accuracy Radial Velocity Planet Searcher) of the 3.6-m telescope at the ESO La Silla Observatory. Offered in October 2003 to the research community in the ESO member countries, this unique instrument is optimized to detect planets in orbit around other stars ("exoplanets") by means of accurate (radial) velocity measurements with an unequalled precision of 1 meter per second.
HARPS was built by a European Consortium  in collaboration with ESO. Already from the beginning of its operation, it has demonstrated its very high efficiency. By comparison with CORALIE, another well known planet-hunting optimized spectrograph installed on the Swiss-Euler 1.2-m telescope at La Silla (cf ESO PR 18/98, 12/99, 13/00), the typical observation times have been reduced by a factor one hundred and the accuracy of the measurements has been increased by a factor ten. These improvements have opened new perspectives in the search for extra-solar planets and have set new standards in terms of instrumental precision.
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