The European Space Agency's Rosetta spacecraft this week began streaming back scientific data from Comet 67P/Churyumov-Gerasimenko as it narrows in on a landing spot for a lander the probe has carried with it on its historic, decade-long journey to the comet.
One instrument on board Rosetta, a NASA surface mapping device dubbed Alice, delivered initial far-ultraviolet observations of Comet 67P/Churyumov-Gerasimenko, known as C-G for short, which "show a surprisingly unreflective surface and lack of water-ice patches," according to scientists at the University of Maryland, College Park.
Researchers working with NASA's Jet Propulsion Laboratory said C-G is "unusually dark—darker than charcoal-black—when viewed in ultraviolet wavelengths," while adding that the space agency's Alice instrumented has "detected both hydrogen and oxygen in the comet's coma, or atmosphere."
"We're a bit surprised at just how unreflective the comet's surface is and how little evidence of exposed water-ice it shows," said Alan Stern, Alice principal investigator at the Southwest Research Institute in Boulder, Colo.
The ESA's spacecraft arrived at Comet 67P/Churyumov-Gerasimenko in early August, following a decade-long journey that carried the probe on a complex, looping course to match the comet's speed and trajectory some 405 million kilometers (252 million miles) from Earth.
Rosetta's historic rendezvous with the comet, a first in spacefaring history, was described by ESA as "opening a new chapter in Solar System exploration."
By mid-September, the ESA expects to announce a landing site target on C-G for Philae, the lander which Rosetta has carried with it since launching in 2004. ESA scientists currently anticipate that Philae will touch down on the comet on Nov. 11, according to Space.com.
In addition to Alice, U.S.-based scientists have contributed several other instruments and support technologies to the total of 11 science instruments aboard Rosetta.