Under a cliff with one foot in the 'air', that's how Philae came to rest on the surface of comet 67P

Data reveal Philae landed in a hole with one foot up

Data from comet lander Philae revealed the pioneering spacecraft ended in a hole after its less than perfect landing in November last year.

Instead of attaching itself firmly to the surface of comet 67P/Churyumov–Gerasimenko with its three harpoon-like feet after the seven-hour descent from the Rosetta orbiter, the washing-machine sized lander bounced off two times and eventually came to rest among large boulders only about a meter away from a high cliff.

The position of the lander, the data published in the latest issue of the Science journal reveal, was also less than perfect, as one of its three feet was pointing upwards.

Philae’s eventual resting site is about a kilometre away from the intended landing location carefully selected by researchers ahead of the descent operation based on good solar illumination as well as suitable conditions for scientific experiments.

The information has been published together with first scientific results from the Phillae mission.

A team from the Universite Paris-Sud in France, states in the paper that Philae seems to be "in a hole about its own size, partially shadowed by nearby boulders or cliffs" with one of its feet stuck in a "local cavity", another rested on a sun-lit surface, and the third "pointing upward".

The researchers added that the site, dominated by “metre-scale blocks, with a large elongated cliff, starting around one metre away” clearly could not provide sufficient illumination to keep the lander going after its primary battery depleted.

Philae’s touchdown on 12 November last year was initially celebrated by spacecraft controllers of the European Space Agency as a major triumph. However, the victory turned sour in only a few hours when it was revealed Philae failed to complete its landing manoeuvre as planned.

Standing partially in the shadow, the lander shut down after only three days of operations, leaving the scientists in uncertainty.

As the comet moved closer to the Sun, the amount of solar radiation reaching the lander increased ans in June it was once again able to contact the Earth via the Rosetta satellite orbiting around the comet.

However, last week Philae controllers at Germany’s Aerospace Centre DLR once again lost contact with the lander.

Despite the setbacks, the whole Rosetta project, is a major success and even though it didn’t go exactly as planned, the Philae landing represents the first time a menmade object was put on a cometary surface in a controlled manner.

The article in Science further describes organic compounds detected by Philae, including some never before found on a comet. Overall 16 organic compounds were detected by Germany’s Cosac instrument. The UK’s Ptolemy detector also found organic compounds on the surface of 67P.

However, no evidence of amino acids, precursors of life, has been found.

Many experts believe comets carried the raw ingredients of life to Earth and other planets in the solar system.

Electromagnetic signals fired through the centre of the comet showed the object has a uniform and highly porous structure. The data also showed the comet is covered with coarse material, rather than dust, and is harder than expected.


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