Russian flight controllers are working to salvage a 15-ton Mars spacecraft that is stranded in a very low orbit around Earth after a botched launch Tuesday.

The probe was expected to be on its way to the Martian moon Phobos to retrieve some soil samples and return them to Earth for analysis. The mission, called Phobos-Grunt (“grunt” is Russian for “soil”) was Russia’s first attempt at planetary exploration since its failed Mars 96 spacecraft.

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An engine firing to send Phobos-Grunt toward Mars never occurred, stranding the spacecraft in a fast and low orbit around Earth that comes as close as 128 miles above planet.

At that altitude, it is only a matter of time before friction from the upper fringes of the atmosphere drags the spacecraft back toward Earth. Most of its mass is toxic rocket fuel, which likely would incinerate at some point during the high-speed descent through the atmosphere.

The spacecraft also contains a small amount of radioactive cobalt-57 in one of its science instruments. It is not known how much of the spacecraft would survive the plunge through the atmosphere or where any debris would land.

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If Russia cannot command Phobos-Grunt to fire its engines to leave for Mars, the spacecraft would become the third and by far largest satellite to re-enter Earth’s atmosphere this year.

The U.S. Space Command, which tracks objects in Earth orbit, has assigned Phobos-Grunt the designation 37872. You can keep track of the spacecraft at

NASA, which on Thursday held a press conference to preview its next Mars spacecraft, the $2.5-billion Mars Science Lab, said it had offered to help Russia with its communications and tracking of Phobos-Grunt.

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“We have offered assistance and if they need it we will provide it to the best of our ability,” NASA’s Mars exploration program head Doug McCuistion told Discovery News.

Image: The ambitious Phobos-Grunt spacecraft was to bring an end to a long string of troubled Russian Mars missions. Credit: Roscomos.