Science & Environment

Philae: Lost comet lander is found

Philae seen from above Image copyright ESA/Rosetta/MPS for OSIRIS Team
Image caption Hello, old friend: Philae (near top right, in darkness) comes back into view

Europe's comet lander Philae has been found.

The little robot is visible in new images downloaded from the Rosetta probe in orbit around the icy dirt-ball 67P/Churyumov-Gerasimenko.

European Space Agency (Esa) officials say there is no doubt about the identification - "it's as clear as day", one told the BBC.

Philae was dropped on to the comet by Rosetta in 2014 but fell silent 60 hours later when its battery ran flat.

Although it relayed pictures and data about its location to Earth, the lander's actual resting place was a mystery.

It was assumed Philae had bounced into a dark ditch on touchdown - an analysis now borne out by the latest pictures, which were acquired from a distance of 2.7km from the duck-shaped icy body.

Wait after comet landing 'bounce'

The images from Rosetta's high-resolution Osiris camera were downlinked to Earth late on Sunday night, and have only just been processed.

Philae is seen wedged against a large over-hang. Its 1m-wide box shape and legs are unmistakable, however.

Image copyright ESA/Rosetta/MPS for OSIRIS Team/NavCam
Image caption The top inset shows the position on the comet; the bottom inset is a blow-up of Philae

Rosetta had previously surveyed this location - dubbed Abydos - without success.

"Candidate detections" were made but none were very convincing.

The difference today is a closer-in perspective and a change in the seasons on the comet, which means the hiding place is now better illuminated.

The discovery comes just a few weeks before controllers plan to crash-land Rosetta itself on to the comet to formally end its investigation of 67P.

Image copyright ESA/Rosetta/MPS for OSIRIS Team
Image caption The robot is on its side, with one of its three legs pointed upwards
Image copyright ESA/ATG medialab
Image caption On its historic landing in 2014, Philae did not make the graceful touchdown depicted here

Although there is no hope of reviving the lander - some of its equipment will have been broken in the cold of space - simply knowing its precise resting place will help scientists make better sense of the data it returned during its three days of operation back in 2014.

"It was very important to find Philae before the mission ended, to understand the context of its in-situ scientific measurements," said Prof Mark McCaughrean, Esa's senior science advisor.

"But it was probably just as important to provide some emotional closure for the millions who have been following both Philae and Rosetta through the trials and tribulations of their exploration of this remarkable remnant of the birth of our Solar System.

"And there's one big final adventure to come on 30 September as Rosetta itself descends to the comet, doing unique science close-up before the mission ends for good," he told BBC News.

Image copyright ESA/Rosetta/Philae/CIVA
Image caption The discovery helps put earlier images like these, from Philae's own cameras, into context

Comet 67P - "Space duck" in numbers

  • A full rotation of the body takes just over 12.4 hours
  • The axis of rotation runs through the "neck" region
  • Its larger lobe ("body") is about 4.1 × 3.3 × 1.8 km
  • The smaller lobe ("head") is about 2.6 × 2.3 × 1.8 km
  • Gravity measurements give a mass of 10 billion tonnes
  • Mapping estimates the volume to be about 21.4 cubic km

Image copyright ESA
Image caption The Rosetta spacecraft arrived at the comet in August 2014 and will end its mission on 30 September

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos

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