When and where will Russia's doomed probe to a Martian moon fall back to Earth? The RIA-Novosti news service caused a stir when it reported that the 13-ton Phobos-Grunt spacecraft would crash in southwestern Afghanistan at 2:22 a.m. Moscow time on Jan. 14. The report attributed the prediction to the U.S. Strategic Command, but experts say it's way too early to be that precise about the Phobos-Grunt debris zone.
"Yes, it is much too early to predict" the circumstances of Phobos-Grunt's re-entry, Gene Stansbery of NASA's Orbital Debris Program Office at Johnson Space Center told me today.
The U.S. Strategic Command is being circumspect as well, deferring comment to NASA and to Roscosmos, Russia's space agency.
The most that can be said about the impact zone right now is that it will be somewhere between 51.4 degrees north and 51.4 degrees south latitude. That's a swath of the planet that stretches from Calgary, Alberta (or Ghent, Belgium) in the north to the Falkland Islands in the south and takes in the vast majority of the world's population. Satellite-watcher Marco Langbroek reports on the See-Sat-L discussion forum that the predicted time of re-entry is Jan. 13, plus or minus 11 days. A couple of weeks ago, Roscosmos estimated that re-entry would come sometime between Jan. 6 and 19.
Typically, the projected area of the debris zone can't be narrowed down until hours before re-entry, if then. It's possible that RIA-Novosti picked up on a prediction that was centered around a precise time and place of re-entry, but left out the part about the plus-or-minus uncertainty. (You can see where Phobos-Grunt is right now by checking the Heavens-Above website.)
The spacecraft was launched from Russia's Baikonur Cosmodrome in Kazakhstan on Nov. 9 local time, and was supposed to leave Earth orbit hours later for the trip to Phobos, the larger of Mars' two moons. Along the way, it would have deployed a Chinese mini-probe in Martian orbit. If everything went well, the $165 million Phobos-Grunt mission would have brought a sample of Phobos soil back to Earth in 2014. ("Phobos-Grunt," or the more correctly transliterated "Fobos-Grunt," is Russian for "Phobos-Soil.")
Everything didn't go well, as we now know: The spacecraft's upper-stage thrusters didn't fire, and it's been stuck in Earth orbit ever since. This month, Russian officials finally gave up on attempts to revive the craft and admitted that it would fall to its destruction next month.
Most of the spacecraft's mass consists of the toxic propellants it would have used to get to Phobos. There's also a small amount of radioactive cobalt-57 that was meant to power a spectrometer. The Russians say that the fuel will burn up in Earth's atmosphere, and that the cobalt won't pose a contamination threat.
Twenty to 30 parts from the probe with a total weight of up to 440 pounds (200 kilograms) are expected to survive the plunge. One of those parts could be the sample return capsule, which is designed to withstand the intense heat of atmospheric re-entry. David Warmflash, the principal investigator for one of the mission's experiments, said "it is quite possible" that his team's LIFE capsule will make it back to Earth intact.
If it lands in Afghanistan, the chances of recovery might be poor, given the proximity to a war zone. But if it lands in the ocean, which is currently the likeliest scenario, the chances aren't any better. Over the past few months, two other high-profile satellites — NASA's Upper Atmosphere Research Satellite and Germany's ROSAT space telescope — fell through the atmosphere over the South Pacific and the Bay of Bengal, respectively, and no trace of them was ever found.
More about Phobos-Grunt and other falls to Earth:
- Mars probe to crash to Earth in January
- Russian leader suggests punishing space failures
- Skywatcher snaps photos of stranded probe
- Christmas Eve fireball sparked by Russian rocket debris
- Russian communications satellite falls after launch
Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.