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Rosetta’s Philae Lander Discovers a Comet’s Organic Molecules Rosetta’s Philae Lander Discovers a Comet’s Organic Molecules
(about 1 hour later)
Philae, the little lost lander that the European Space Agency dropped on a comet last November, is still lost.Philae, the little lost lander that the European Space Agency dropped on a comet last November, is still lost.
Although it woke up last month and has made contact several times with the Rosetta orbiter, which is examining Comet 67P/Churyumov-Gerasimenko from miles away, Philae has not been heard from for more than two weeks, and the sporadic communications have not been long enough for the lander to resume its scientific work.Although it woke up last month and has made contact several times with the Rosetta orbiter, which is examining Comet 67P/Churyumov-Gerasimenko from miles away, Philae has not been heard from for more than two weeks, and the sporadic communications have not been long enough for the lander to resume its scientific work.
But even the 60 hours of observations it conducted immediately after landing have provided an intriguing wealth of data about the composition, structure and properties of the comet, described in detail in seven papers published Thursday by the journal Science.But even the 60 hours of observations it conducted immediately after landing have provided an intriguing wealth of data about the composition, structure and properties of the comet, described in detail in seven papers published Thursday by the journal Science.
Jean-Pierre Bibring, the lead scientist for the Philae lander, highlighted the discovery of large dark grains, a millimeter or more wide, which appeared to be made of complex light-absorbing organic molecules. “This is fundamental,” Dr. Bibring said. “We didn’t know that.”Jean-Pierre Bibring, the lead scientist for the Philae lander, highlighted the discovery of large dark grains, a millimeter or more wide, which appeared to be made of complex light-absorbing organic molecules. “This is fundamental,” Dr. Bibring said. “We didn’t know that.”
Organic, carbon-based molecules are thought to be the building blocks for life but can come together in nonbiological chemical reactions. These molecules, Dr. Bibring said, formed in the cold of space, possibly even before the grains clumped together to become the comet.Organic, carbon-based molecules are thought to be the building blocks for life but can come together in nonbiological chemical reactions. These molecules, Dr. Bibring said, formed in the cold of space, possibly even before the grains clumped together to become the comet.
The bouncing landing itself provided data that the scientists would not otherwise have obtained.The bouncing landing itself provided data that the scientists would not otherwise have obtained.
Philae, the size of a washing machine, landed on Comet 67P almost exactly where it had aimed. But a downward-pushing thruster failed to fire and two harpoons meant to secure the lander to the surface also did not deploy. Philae bounded back into space. It scraped the rim of a crater and bounced a second time off the surface before settling awkwardly in a smaller crater, in the shadow of a cliff without sufficient sunlight for its solar panels to recharge its battery. Philae, the size of a washing machine, landed on Comet 67P almost exactly where it had aimed. But a downward-pushing thruster failed to fire, and two harpoons meant to secure the lander to the surface did not deploy. Philae bounded back into space. It scraped the rim of a crater and bounced a second time off the surface before settling awkwardly in a smaller crater, in the shadow of a cliff without enough sunlight for its solar panels to recharge its battery.
At the targeted landing site, the feet of the lander sank about 10 inches into a soft granular material that absorbed much of its kinetic energy. Stephan Ulamec, the project manager for Philae, likened it to landing in a sandbox.At the targeted landing site, the feet of the lander sank about 10 inches into a soft granular material that absorbed much of its kinetic energy. Stephan Ulamec, the project manager for Philae, likened it to landing in a sandbox.
But at the final resting place, the comet proved unexpectedly hard — at least as hard as compacted snow — and the lander was unable to hammer in a sensor rod to measure temperatures below the surface.But at the final resting place, the comet proved unexpectedly hard — at least as hard as compacted snow — and the lander was unable to hammer in a sensor rod to measure temperatures below the surface.
“That was a surprise to us,” said Tilman Spohn, the principal investigator for that instrument. “We didn’t think it would be that hard.”“That was a surprise to us,” said Tilman Spohn, the principal investigator for that instrument. “We didn’t think it would be that hard.”
But the scientists also know that the material is highly porous. Dr. Spohn said the measured thermal properties were consistent with a hard ice layer covered by an inch or so of dust.But the scientists also know that the material is highly porous. Dr. Spohn said the measured thermal properties were consistent with a hard ice layer covered by an inch or so of dust.
About 20 minutes after the first touchdown, in the middle of the first jump across the surface, two similar instruments took a sniff of the surroundings to identify molecules in the vicinity. One detected four organic compounds that had never been seen emanating from a comet. The other detected chains of formaldehyde molecules. Those are probably just hints of more complex organic molecules.About 20 minutes after the first touchdown, in the middle of the first jump across the surface, two similar instruments took a sniff of the surroundings to identify molecules in the vicinity. One detected four organic compounds that had never been seen emanating from a comet. The other detected chains of formaldehyde molecules. Those are probably just hints of more complex organic molecules.
“It’s clearly got a story to tell,” said Ian P. Wright, the principal investigator for one of the instruments.“It’s clearly got a story to tell,” said Ian P. Wright, the principal investigator for one of the instruments.
In appearance, Comet 67P has proved to be quite strange and varied, with a two-lobed shape resembling a rubber duck and a range of terrains. But a radar experiment, sending a signal from Philae to the Rosetta orbiter through the comet, revealed that the material, at least within the head portion, was fairly homogeneous beneath the surface.In appearance, Comet 67P has proved to be quite strange and varied, with a two-lobed shape resembling a rubber duck and a range of terrains. But a radar experiment, sending a signal from Philae to the Rosetta orbiter through the comet, revealed that the material, at least within the head portion, was fairly homogeneous beneath the surface.
If Philae comes to life again, the landing acrobatics may yet turn out to be more blessing than curse.If Philae comes to life again, the landing acrobatics may yet turn out to be more blessing than curse.
Had it landed as planned, Philae would have overheated and died by the spring. But instead it is in a cooler, more protected spot, and engineers expected it to wake up when more light reached its solar panels as Comet 67P came closer to the sun.Had it landed as planned, Philae would have overheated and died by the spring. But instead it is in a cooler, more protected spot, and engineers expected it to wake up when more light reached its solar panels as Comet 67P came closer to the sun.
Philae indeed woke up June 13, but communication has been intermittent. Mission controllers were encouraged by 12 minutes of interrupted transmissions between Philae and the Rosetta orbiter on July 9, but it has been out of touch since.Philae indeed woke up June 13, but communication has been intermittent. Mission controllers were encouraged by 12 minutes of interrupted transmissions between Philae and the Rosetta orbiter on July 9, but it has been out of touch since.
Dr. Ulamec said the position of Philae may have shifted, its antenna perhaps blocked, and there appeared to be a problem with at least one of its transmitters. Otherwise the lander seemed to be in good condition.Dr. Ulamec said the position of Philae may have shifted, its antenna perhaps blocked, and there appeared to be a problem with at least one of its transmitters. Otherwise the lander seemed to be in good condition.
Meanwhile, the Rosetta orbiter has continued its observations of the comet, examining, for example, how the outpourings of gas interact with the wind of high-speed particles from the sun. At present, it has moved to take a closer look at the southern hemisphere of the comet, which is emerging from shadow into sunlight. The current position, where the comet itself blocks any radio transmissions, makes it impossible to hear anything from Philae even if Philae were broadcasting, but next week Rosetta will return north and listen again.Meanwhile, the Rosetta orbiter has continued its observations of the comet, examining, for example, how the outpourings of gas interact with the wind of high-speed particles from the sun. At present, it has moved to take a closer look at the southern hemisphere of the comet, which is emerging from shadow into sunlight. The current position, where the comet itself blocks any radio transmissions, makes it impossible to hear anything from Philae even if Philae were broadcasting, but next week Rosetta will return north and listen again.
“I’m an optimist,” Dr. Ulamec said. “I think we should have contact again.”“I’m an optimist,” Dr. Ulamec said. “I think we should have contact again.”
In two weeks, on Aug. 13, Comet 67P will make its closest approach to the sun, some 115 million miles away, halfway between the orbits of Earth and Mars.In two weeks, on Aug. 13, Comet 67P will make its closest approach to the sun, some 115 million miles away, halfway between the orbits of Earth and Mars.
As to where Philae is precisely, nobody knows for sure.As to where Philae is precisely, nobody knows for sure.
Triangulation of the radar signals has narrowed the position to an area about 110 feet by 70 feet. Rosetta’s cameras have spotted glints of light that could be Philae. The location might not be confirmed until late next year, when Comet 67P has moved away from the sun, and Rosetta can descend for a closer look.Triangulation of the radar signals has narrowed the position to an area about 110 feet by 70 feet. Rosetta’s cameras have spotted glints of light that could be Philae. The location might not be confirmed until late next year, when Comet 67P has moved away from the sun, and Rosetta can descend for a closer look.
By then, Philae will certainly be dead, but that information could retroactively refine the measurements the scientists already possess.By then, Philae will certainly be dead, but that information could retroactively refine the measurements the scientists already possess.