Hope is fading for the Russian Phobos-Grunt mission to Mars, as the probe has been trapped in low Earth orbit since Wednesday. The 13-ton (11.8-tonne) unmanned spacecraft was launched from the Baikonur Cosmodrome in Kazakhstan on November 9, atop a Ukrainian Zenit-2 booster. Baikonur ground control lost track of the probe when it failed to appear in its predicted orbit. According to the Russian Space Agency, the Phobos-Grunt's engines failed to fire twice, leaving the probe in a low, rapidly decaying orbit. Despite continuing efforts, ground control has been unable to get the probe to respond to commands and can only receive telemetry data from it. If the Russians are unable to regain control, the Phobos-Grunt is expected to make an uncontrolled re-entry into the Earth's atmosphere, along with its 8.3 tons (7.5 tonnes) of highly toxic propellant and radioactive cobalt-57.

The cause of the Phobos-Grunt's failure to fire its engines still remains unknown. Russian officials continue to hope that the problem is a software glitch, which means that ground control can reprogram the computers and attempt to fire the engines again. However, if the problem is in the hardware, then the mission is a failure. Originally, the Russian Space Agency was only able to signal the probe while it passed over Baikonur or a ground station near Moscow, but NASA and the European Space Agency have offered their help in trying to maintain contact. The one bright spot is that the solar panels aboard the machine have been confirmed as deployed, otherwise the onboard batteries would have been exhausted in a little over three days.

Mission to Phobos

At 13.2 tons, the Phobos-Grunt (Grunt means "earth," "dirt" or "ground" in Russian) is the largest deep-space probe since the American Cassini spacecraft was launched to Saturn was launched in 1997. The US$163 million mission was intended to be Russia's return to the high table of space exploration. The first Russian deep-space probe in 15 years, the objective of the bus-sized craft is, as the name implies, to orbit Phobos - one of the tiny moons of Mars, that some scientists suspect are captured asteroids. Once on station, the probe would release a landing craft that would descend to the moon's surface, collect soil samples and then launch a return vehicle containing seven ounces (200 g) of dirt to Earth for recovery in 2014. In addition, the Phobos-Grunt would deploy the Chinese Mars orbiter Yinghuo-1 - China's first deep-space mission.

On a more controversial note, part of the Phobos-Grunt science package is a biological experiment devised by America's Planetary Society, which is designed to study the effects of deep-space travel on samples of bacteria, plant seeds and microorganisms known as water bears. Some critics have stated that the inclusion of living creatures violates international space treaties because of the danger of the probe crashing on Mars and contaminating the environment, but the Russians have replied that the chances of this occurring and the safeguards used make this likelihood too remote to be regarded as such.

At any rate, all such worries are moot so long as the Phobos-Grunt remains trapped in Earth orbit. As it stands, there are three possible outcomes. First, the engines can be fired and the mission proceeds with a slight delay. Second, the engines don't fire. If this happens, the probe will lose 1.25 miles (2 km) of altitude a day until it burns up in the Earth's atmosphere with a month. Third, the engines fire, but the probe misses the two-week launch window, in which case it will never reach Mars.

As things stand, an uncontrolled re-entry seems the most likely outcome. According to the Russian news service Interfax (article in Russian), the chances of success are "negligible," with the Russian armed forces' former chief space adviser Vladimir Uvarov stating "Based on my experience, you cannot make the upper-stage work on a second attempt." He went on to say more bluntly, "I think we have lost the Phobos-Grunt."

Space program at stake

Despite this, the Russians continue to try. Part of the reason is that the past year in space has been a disastrous for them. With the loss of three satellites on launch in December 2010, another in February 2011, a third in August, and the crash of a Progress cargo ship en route to the International Space Station less than a week later, morale among Russian space scientists and confidence of Russia's launch customers was on the floor. Phobos-Grunt was their chance for a comeback, and if it fails, Russian sources are already talking about mass resignations, sackings and restructuring.

Worse, the "Mars Curse" has been revived. Mars missions have a terrible reputation for failure, with over half of them ending in disaster. Half of those failures over the past fifty years have been Russian, with the only real success dating back to 1973. Their last attempt was in 1996, and that ended up in the Pacific Ocean. Therefore, a lot is riding on the success of this mission and, however slim the odds, the Russians are determined to play their hand until the end.