Philae Silence Dashes Hopes
Optimism evaporates as host comet nears Sun…
The optimistic expectations, triggered by a message on June 13 from the long-dormant lander Philae which went into hibernation after a problematic descent to a shady spot which drained it of power on comet 67P/Churyumov –Gerasimenko last November, appear to be replaced by frustration and disappointment as the comet nears its closest approach to the Sun.
Released by the European Space Agency’s (ESA) Rosetta spacecraft onto the comet on November 12 after an epic 10-year chase, the lander had bounced twice when the retrorocket to press it down and harpoons on its legs to anchor it to the surface failed to deploy, ending up at the foot of a cliff which largely blocked the sunlight to power its batteries. From the images sent by the lander, ESA experts had deduced that it was lying on one of its solar panel-covered sides as seen in the artists’ conception above.
A 85-second-long communication from Philae via Rosetta orbiting the comet on June 13 after seven months of silence had raised hopes at ESA that the lander may get back to work. But after a number of brief signals, the last of which was received on July 9, Philae returned to its silence.
ESA technicians think two of the lander’s transmitters and one of its receivers are defunct.
67P/Churyumov-Gerasimenko is expected to arrive at its nearest point to the Sun on August 13.
Before its batteries went flat, Philae had gathered as much data as it could and carry out most of its pre-programmed task for nearly three days despite its awkward position, sending the priceless data back to Earth via its mothership Rosetta.
Results obtained from the perusal of the data was published in the July 31 issue of Science as a six-paper special section.
Among the most interesting is the finding that 67P/Churyumov-Gerasimenko (and presumably others, too) is more a dirt-ball, belying the long-sustaining “dirty snowballs” epithet. Data show that the comet’s surface is covered more with dust than ice. The dust is thought to be flung to the space from under the surface by jets of sublimating ices and then settling on the surface, attracted by the comet’s weak gravity. Beneath the 20-cm thick dust layer, the comet is found to have a relatively harder cocoon, formed of dust glued together by the UV radiation from the Sun, encasing a “hollow” interior of low-density rubble.
- 1. “Philae’s scientific harvest may be its last”, ScienceOnline, 30 July 2015.