EcoAlert: Russians Preparing for Re-entry of Failed Probe of Mars’ Mystery Moon Phobos


Russia's $163 million Phobos-Grunt Mars probe, stuck in low-Earth orbit after a malfunction following launch Nov. 8, is expected to fall back into Earth's atmosphere next month, Russian officials confirmed Friday. Whenever it falls, this will be the third uncontrolled re-entry of a large satellite since September. NASA's 6.3-ton Upper Atmosphere Research Satellite fell back to Earth late Sept. 23 U.S. time, showering debris harmlessly into the south Pacific Ocean, and wreckage from Germany's 1.7-ton ROSAT X-ray telescope fell without incident into the Bay of Bengal on Oct. 23.

The massive spacecraft, still loaded with 11 tons of rocket fuel, will burn up during entry, but 20 to 30 pieces of debris, totaling several hundred pounds, are expected to survive atmospheric heating, hitting the ground somewhere between 51.5 degrees to either side of the equator.

The spacecraft is stranded in an 89.2-minute orbit with a low point, or perigee, of 125 miles and a high point, or apogee, of 171 miles. The Russian space agency Roscosmos said re-entry is expected between Jan. 6 and 19. Ted Molczan, a respected independent satellite tracking expert, calculates entry will occur around Jan. 11, plus or minus 5 days.

Roscosmos and the Russian defense ministry have set up a task force to monitor Phobos-Grunt's trajectory and eventual fall to Earth. The agency said the spacecraft's propellant — highly toxic nitrogen tetroxide and dimethylhydrazine rocket fuel — will burn up in the atmosphere and poses no threat to the public. Likewise, the agency said that 10 micrograms of radioactive Cobalt-57, used in one of the spacecraft's experiments, would not pose a health threat or have any adverse environmental threat.

Perched atop a two-stage Zenit-2 rocket, Phobos-Grunt was launched Nov. 8 from the Baikonur Cosmodrome in Kazakhstan. It successfully reached its preliminary parking orbit, but the spacecraft's main propulsion module, or MDU, did not ignite as expected for the first of two "burns" to boost the craft onto an interplanetary trajectory to Mars.

The probe's solar arrays apparently deployed as planned, indicating the spacecraft had power and was not limited to on-board batteries. Amateur satellite trackers said Phobos-Grunt appeared to be steady and not flashing as one would expect if it was tumbling. But a throw-away fuel tank that normally would have been jettisoned after the initial Earth-departure rocket firing apparently remained in place, possibly blocking a critical low-gain antenna.

Engineers made multiple attempts to communicate with the spacecraft during passes over Russian ground stations, sending commands to initiate contact and perhaps to reboot the flight computer. European Space Agency ground stations also were used to "listen" for telemetry and to send commands in hopes of establishing communications.

On Nov. 21, the launch window for a normal trajectory to Mars closed, ending any chance for the planned mission even if the spacecraft could be recovered. The next night, an ESA ground station in Perth, Australia, finally heard signals from Phobos-Grunt, according to Anatoly Zak's RussianSpaceWeb, but it's not clear whether any meaningful data was received then or during a handful of subsequent contacts.

Phobos-Grunt was the first interplanetary spacecraft launched by Russia since 1996 when an ambitious Mars mission was lost in a launch failure. Of the 19 unmanned Russian Mars missions launched prior to Phobos-Grunt, 15 were outright failures. NASA's record currently stands at 13 successes in 18 previous missions, not counting the $2.5 billion Mars Science Laboratory, which was launched toward the red planet Nov. 26.

Phobos-Grunt was expected to reach Mars in October 2012. The flight plan called for the spacecraft to jettison its propulsion module, used for trajectory correction maneuvers and to brake into orbit, and release a small Chinese orbiter.

The main aim of the Phobos-Grunt mission was to bring back the first ever soil sample from Phobos, the larger of Mars' two moons. According to the original plan, Phobos-Grunt should reach Mars in 2012 and then deploy its lander for Phobos in 2013 before returning the sample back to Earth in August 2014.

Phobos, which orbits Mars at a radius of just under 10,000 kilometres, is believed to be the closest moon to its planet anywhere in the solar system and scientists hope it will reveal secrets about the origins of the planets.

The probe is carrying numerous international experiments including a capsule of microbes prepared by the US Planetary Society to see if basic life forms can survive on a long mission in deep space.

Phobos-Grunt was to have been launched in 2009 but the date was put back until 2011, the soonest possible launch window when the planet's relative proximity to Earth makes a voyage feasible.

Earlier this year, ESA's Mars Express performed a special manouvre to observe an unusual alignment of Jupiter and Phobos. The impressive images have now been processed into a movie of this rare event. The origin of Phobos (which means "fear" in ancient Greek), is a mystery, but three theories are considered plausible.

The first is that the moon is a captured asteroid; the second is that it formed in-situ as Mars formed below it, and the third is that Phobos formed later than Mars, from debris flung into martian orbit when a massive meteorite struck the Red Planet. A fourth, far more radical and controversial (although thoroughly intriguing) theory is one that has been kicking around for decades: that Phobos is a artificial object in Mars orbit -in short, a 1.5-mile-long, extremely ancient spacecraft.

In a new development, scientists say they have uncovered firm evidence that Mars's largest moon, the mysterious Phobos, is made from rocks blasted off the Martian surface in a catastrophic event, solving a long-standing puzzle. It has been suggested that both Phobos and Deimos could be asteroids that formed in the main asteroid belt and were then "captured" by Mars's gravity.

An alternative theory suggests that Phobos could have been formed from the remnants of an earlier moon destroyed by Mars's gravitational forces. However, this moon might itself have originated from material thrown into orbit from the Martian surface.

Previous observations of Phobos at visible and near-infrared wavelengths have been interpreted to suggest the possible presence of carbonaceous chondrites, found in meteorites that have crashed to Earth. This carbon-rich, rocky material, left over from the formation of the Solar System, is thought to originate in asteroids from the so-called "main belt" between Mars and Jupiter.

New data from the European Space Agency's Mars Express spacecraft appears to make the asteroid capture scenario look less likely. Recent observations as thermal infrared wavelengths using the Planetary Fourier Spectrometer (PFS) instrument on Mars Express show a poor match between the rocks on Phobos and any class of chondritic meteorite known from Earth, which seems to support the "re-accretion" models for the formation of Phobos, in which rocks from the surface of the Red Planet are blasted into Martian orbit to later clump and form Phobos.

"We detected for the first time a type of mineral called phyllosilicates on the surface of Phobos, particularly in the areas northeast of Stickney, its largest impact crater," said co-author Dr Marco Giuranna, from the Italian National Institute for Astrophysics in Rome.These phyllosilicate rocks are thought to form in the presence of water, and have been found previously on Mars.

"This is very intriguing as it implies the interaction of silicate materials with liquid water on the parent body prior to incorporation into Phobos," said Dr Giuranna. "Alternatively, phyllosilicates may have formed in situ, but this would mean that Phobos required sufficient internal heating to enable liquid water to remain stable."

Other observations from Phobos appear to match the types of minerals identified on the surface of Mars. Thus, the make-up of Phobos appears more closely related to Mars than to asteroids from the main belt, say the researchers.

In addition, said Pascal Rosenblatt of the Royal Observatory of Belgium, "the asteroid capture scenarios also have difficulties in explaining the current near-circular and near-equatorial orbit of both Martian moons (Phobos and Deimos)".

The researchers also used Mars Express to obtain the most precise measurement yet of Phobos' density. "This number is significantly lower than the density of meteoritic material associated with asteroids. It implies a sponge-like structure with voids making up 25%-45% in Phobos's interior," said Dr Rosenblatt.

A highly porous asteroid would have probably not survived if captured by Mars. Alternatively, such a highly porous structure on Phobos could have resulted from the re-accretion of rocky blocks in Mars' orbit.

Describing the internal geometric structure of this "moon" as revealed by MARSIS, European Space Agency (ESA) sources emphasized that "several of these interior Phobos compartments also appear to still be holding some kind of atmosphere …." which has given birth to wild speculation that Phobos could prove to be an artificial satellite of some sort. The source repeated this several times … raising all kinds of fascinating questions regarding "how" the radar could, in fact, determine this — that some of the vast "rooms" inside Phobos ("from a quarter to half-a-mile in diameter …") were "maintaining an internal pressure."


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