Updated at 3 p.m. ET Updated at 3 p.m. ET A satellite designed to hunt for mysterious methane and other gases in the atmosphere of Mars looped itself into an egg-shaped, four-day orbit around the Red Planet on Wednesday, while anxious flight directors awaited word on whether a companion lander survived its touchdown.
Trace Gas Orbiter (TGO) joins a fleet of five satellites and two rovers currently operational at Mars, the planet most like Earth in the solar system.
Sniffing out methane is tied to a larger European-Russian initiative, with participation by NASA, to learn if there is past or present day life on Mars. Methane on Earth is strongly tied to biological activity.
Methane has been detected on Mars, and has on occasion appeared as a plume, but the gas disappears far more quickly than current theories can account for.
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TGO, which spent seven months traveling to Mars, was accompanied by a small lander, called Schiaparelli, which spent the last three days on a solo flight toward the planet's surface.
Radio signals relayed by Europe's Mars Express satellite show that Schiaparelli descended through the atmosphere as planned, with its parachutes opening and followed by release of a protective backshell, said Don McCoy, manager of the ExoMars project.
But whether the lander survived touchdown was still a mystery. An upcoming data link with NASA's Mars Reconnaissance Orbiter (MRO), and more analysis from Mars Express signals, should provide some answers on Thursday, ESA said.
"We saw the signal through the atmosphere phase, and at a certain point the signal stopped," said Paolo Ferri, ESA head of mission operations.
Analysis of data from Mars Express showed the same pattern, he added. "It is clear that these are not good signs."
Even if Schiaparelli crashed, ESA says the project will still provide valuable information for landing a much bigger spacecraft on Mars in 2021. The ExoMars rover is an ambitious mission to search for past or present-day life on Mars.
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"The landing was a test, and as part of the test you want to learn what happened," Ferri said. "I'm quite confident that by (Thursday) morning we will know."
TGO plays a vital role in the upcoming rover mission as well, serving as a communications link to back up the 13-year-old Mars Express. NASA too will look to use TGO to supplement its own aging communications orbiters, the 15-year-old Mars Odyssey and the 11-year old MRO.
NASA also operates the MAVEN spacecraft, which is studying atmospheric loss in hopes of learning why Mars lost its water.
Schiaparelli was due to touch down near where one of NASA two operational rovers are working, in the Meridiani Planum region of Mars.
The flat, low-lying site, located 2 degrees south of the equator, was specifically selected so Schiaparelli could fly through as much atmosphere as possible before coming to a rest on the surface.
The lander was designed to drop the final few yards to the ground and was outfitted with a crushable structure, similar to a car's crumple zone, to absorb the final forces of impact.
Schiaparelli is only the second spacecraft that Europe has attempted to land on Mars. A United Kingdom-led effort called Beagle 2 failed during touchdown on Dec. 25, 2003.
It was later discovered to have survived the landing, but was unable to communicate because its antenna was blocked by solar panels that failed to fully deploy.
Image: Artist's illustration of Europe's Trace Gas Orbiter getting into position around Mars. Credit: ESA/ATG medialab WATCH VIDEO: Will ExoMars Find Life on the Red Planet?