Russia's space agency admitted it was racing the clock today to save its ambitious Mars probe, Phobos-Grunt, which was meant to bring back soil from the Martian moon Phobos, but instead is stranded in low Earth orbit.
Sources told ABC News efforts to send corrective computer code to the ship's flight controller have failed because they have not been able to communicate with the spacecraft.
"I think we have lost the Phobos-Grunt," Vladimir Uvarov, a former top space expert at the Russian Defense Ministry, said in an interview Thursday in the government daily Rossiyskaya Gazeta. "It looks like a serious flaw. The past experience shows that efforts to make the engines work will likely fail."
Phobos-Grunt (the word "Grunt" is a translation of "ground") was launched into Earth orbit from Kazakhstan at 3:16 p.m. ET Tuesday. The plan was for its upper stage then to boost it on the long flight to Mars, where it was intended to go into orbit in September 2012. It was supposed to land on Phobos in February 2013, scoop up about 7 ounces of soil, and bring it back to Earth in August 2014.
But Ted Molczan, a Canadian satellite observer, said the upper stage never fired. It was supposed to start automatically, out of range of Russian communications stations on the ground. Molczan says the ship is in a low elliptical orbit, ranging between 129 and 212 miles from Earth.
If the Russians can isolate the problem -- and it turns out to be something that can be corrected by remote control -- perhaps the mission can be saved. But if too much time passes, Mars will gradually move beyond where the ship, with a finite fuel supply, can reach. And in the meantime, Earth's atmosphere will gradually slow it from orbit.
"Decay from orbit is not imminent, with the caveat that the spacecraft's rate of orbital decay has yet to be determined with precision," said Molczan in an email to ABC News. "Using the most current orbital elements issued by the U.S. Strategic Command, I estimate decay from orbit within about a week of Dec 18, 2011."
The United States does not have a part in the mission, but the U.S. Space Surveillance Network was tracking the spacecraft and its booster, still in orbit behind it.
"If control of the spacecraft is not regained, then it will fall back to Earth in an uncontrolled manner," said Nicholas Johnson of NASA's orbital debris program in an email. "Due to its large mass, one could reasonably assume that some debris will survive to the surface of the Earth. The same can also be said for the large launch vehicle stage which is also in a very low orbit. Both vehicles are significantly more massive than UARS was."
UARS, the American Upper Atmosphere Research Satellite, crashed in the Pacific in September. It weighed six tons and had several components believed sturdy enough to survive re-entry, so NASA was very public about projecting its path in its final days. Phobos-Grunt has a mass of 14.6 tons, and parts could crash to Earth, but engineers say that like most spacecraft, it would most likely crash in the ocean (70 percent of the planet's surface) or unpopulated land.
The Russians, working with Germany's DLR space lab, were trying for a major first. Phobos, named for the Greek god of fear, is only 15 miles across, but it is the larger of Mars' two known moons. It may be an asteroid that was captured by the gravity of Mars eons ago, and scientists would very much like to know what it is made of.
Apollo astronauts, and one Soviet probe, have brought back 800 pounds of rock and soil from the moon. And an American probe called Stardust returned minute samples from the tail of a comet in 2006. But Mars and its moons have been seen as the next destination in space.
NASA's Opportunity rover, which landed on Mars in 2004, is still working, and a new, larger one, called Curiosity, is scheduled for launch Nov. 25. In the half century since the space age began, the Russian space program has tried and failed repeatedly to reach Mars.
Gina Sunseri of ABC News contributed reporting. Additional information from The Associated Press.