Despite rocky start, Philae probe has raked in science data


Twelve years ago, the European Space Agency launched a spacecraft with a very precious cargo — a robot laboratory designed to land on a comet and photograph, prod and sniff its surface.

The €1.3-billion ($1.5-billion) mission of robot lab Philae and its orbiting mothership, Rosetta, was to shed light on the solar system’s formation, and possibly the origins of life on Earth. While Rosetta will remain with comet 67P/Churyumov-Gerasimenko until September, scientists on Feb. 12 bade farewell to Philae from which there has been no word for seven months.

These are some of Philae’s contributions to science.

The lander’s COSAC gas analyzer sniffed the dust kicked up by Philae’s comet ricochet, and identified 16 different carbon-containing organic compounds — found in all living things. Another instrument, Ptolemy, detected water vapor, carbon monoxide and carbon dioxide in the comet’s hazy “coma,” as well as organic compounds such as formaldehyde.

Comets are believed to contain materials left over from the solar system’s formation some 4.6 billion years ago, and scientists see them as time capsules that may provide insights into Earth’s own origins. One theory is that comets smashed into our infant planet, providing it with precious water and the chemical building blocks for life.

Many had feared that Philae would land on a soft and fluffy surface, possibly even sink. Instead it bounced when its harpoons failed to fire.

This very rebound, though unintended, allowed scientists to compare the surface characteristics of the spot where Philae first touched down, dubbed Agilkia, and where it finally settled, Abydos.

The lander’s ROLIS camera captured a dark, nonreflective surface littered with pebbles and rocks ranging from a few centimeters across to 5 meters. There was much less water ice than expected.

While the surface at Agilkia was relatively soft, Philae’s MUPUS hammer failed to break the surface at Abydos, where it conducted its experiments.

Under a thin dust layer just a few centimeters thick, MUPUS slammed into super-dense mixture of compacted dust and ice.

The hardness of the surface was the “biggest surprise” of 67P, the German Aerospace Centre DLR, which hosts the lander control centre, has said.

In contrast, the CONSERT radar instrument found that inside, the 10-billion-ton comet was made of a very loosely compacted mix of dust and ice — so porous it would float on water on Earth.