A large Russian interplanetary spacecraft is in low earth orbit carrying about 10 tons of unsymmetrical dimethylhydrazine and nitrogen tetroxide. These toxic compounds were supposed to be used as fuel by the spacecraft on its long voyage to and from Mars. The spacecraft was to launch a probe toward the Martian surface and scoop up a sample of soil and fly it back to Earth. Therefore, the Phobos-Grunt mission to Mars needed a large amount of fuel as a part of its payload package.
The Russian Phobos-Grunt Mars mission lifted off on November 8th, and should already have escaped the Earth’s orbit. But it is still lingering in low Earth orbit while scientists are trying to determine why a rocket that would have flung the spacecraft towards Mars did not fire. The spacecraft was able to break away from the booster rocket that was used during lift-off. But a secondary rocket that would have sent the spacecraft and probe to the red planet did not ignite.
Scientists are not sure whether the secondary rocket launch failure was due to a hardware or software malfunction. They have been trying to send new instructions to the Phobos-Grunt’s computer, but have been unsuccessful.
The alternate spelling of the Russian mission to Mars is Fobos-Grunt. In English it translates to “Phobos-Soil” or “Phobos-Ground” which ties directly in with the primary objective of the Mars mission to return a soil sample back to Earth.
If Russian scientists are not able to recover communications with Phobos-Grunt the spacecraft could plunge into the Earth’s atmosphere toward the end of November. Some of the toxic substance will burn up on re-entry. However, some toxic material from the Russian satellite will reach the ground. The spacecraft and its toxic cargo is expected to make re-entry somewhere between 55 degrees north and 55 degrees south of the equator.
Source:
http://www.foxnews.com/scitech/2011/11/11/toxic-russian-mars-probe-heading-back-to-earth/?test=latestnews
http://en.wikipedia.org/wiki/Fobos-Grunt