16 September 2014
By JoAnna Wendel
Scientists expect to present preliminary results from the first spacecraft to land on a comet at the American Geophysical Union’s Fall Meeting in December. That’s assuming, of course, that they first succeed at dropping a lander from thousands of meters away onto a tiny comet – a feat never tried before.
The Rosetta mission is the first designed to orbit and land on a comet, according to the European Space Agency. The mission’s Philae lander will touch down at candidate site “J” at the head of comet 67/P Churyumov-Gerasimenko on 12 November, the ESA announced Monday morning after weeks of deliberation.
Scientists expect to have preliminary results from the lander by the time scientists, journalists, educators and others gather for the AGU’s Fall Meeting from December 15-19 in San Francisco, according to US Rosetta Project Scientist Claudia Alexander of NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
Rosetta reached the comet last month after 10 years in flight and multiple gravity assists by Earth and Mars that boosted the spacecraft’s velocity and altered its trajectory. Since then, project scientists have hurried to find a landing spot that will be both accessible and safe.
Site J was unanimously chosen for its unique scientific potential and the minimal risk it poses to the lander compared to other possible landing sites, according to ESA. Once Philae touches down, it will immediately drill into the comet’s surface to collect material that will be analyzed by various onboard instruments. Meanwhile, Rosetta’s orbiter will continue to monitor the comet from about 10 kilometers (about six miles) away, analyzing the gases and other material that is ejected from the space rock.
Alexander hopes the lander’s investigations will reveal details about the makeup of the comet itself—its geology, how the comet formed, and how its origins could relate to the origins of planetary formation.
Preliminary observations from the orbiter already have scientists excited. “It’s the weirdest extraterrestrial material ever—as black as the toner you use in your school printers,” Alexander said. Despite how primordial the comet is, it has more complex geology than you might expect, she added.
Before scientists will have any results to pore over, Philae must first safely land on the comet, which promises to be extremely tricky, according to Alexander.
Alexander said it will likely be more suspenseful than the seven minutes of terror scientists experienced when Curiosity touched down on Mars two years ago. She said the landing could take up to seven hours.
“We’re going to have an indeterminate number of hours of terror,” Alexander said. “[This] is going to have our engineers biting their fingernails the whole time.”
“We’re dropping something from a height at which a 747 flies above the Earth onto something that’s the size of central park in New York [City],” Alexander said. Because of the comet’s weak gravity field, “it’s like dropping a piece of paper.”
After making it onto the comet, the lander will initially be in continuous operation for three days using its primary batteries and will then operate on and off for another few months on its secondary batteries, according to Alexander. By March of 2015, as comet 67/P Churyumov-Gerasimenko nears the sun, “we expect the lander to be too warm for operation,” Alexander said, “[and] once it goes off, we won’t use it again.”
A co-convener of sessions at the meeting about Rosetta, Alexander said there will be two oral sessions at the AGU Fall Meeting focused on what scientists have learned from the orbital mission, and one session dedicated to what they’ve learned from the lander.
— JoAnna Wendel is a staff writer for the AGU’s weekly newspaper, Eos. She primarily writes Research Spotlights, short summaries highlighting exciting research from AGU’s journals