ESA's Rosetta ends its historic 12-year mission with touchdown on comet 67P

The Rosetta mission on Friday ended its mission in a controlled descent of the spacecraft onto the surface of comet 67P/Churyumov-Gerasimenko.

New Delhi: The European Space Agency (ESA)'s Rosetta space probe, which has been tracking a comet for the past two years, has landed on the comet, ending its 12-year  mission.

The Rosetta mission ended its historic mission in a controlled descent of the spacecraft onto the surface of comet 67P/Churyumov-Gerasimenko at around 7:20 a.m. EDT Friday. 

Confirmation of the end of the mission arrived at ESA's control centre in Darmstadt, Germany, with the loss of Rosetta's signal upon impact, the ESA said in a statement.

For its final manoeuvre, Rosetta had targeted a region on the small lobe of Comet 67P/Churyumov-Gerasimenko, close to a region of active pits in the Ma'at region.

The descent gave Rosetta the opportunity to study the comet's gas, dust and plasma environment very close to its surface, as well as take very high-resolution images.

Pits are of particular interest because they play an important role in the comet's activity. They also provide a unique window into its internal building blocks.

The information collected on the descent to this fascinating region was returned to the Earth before the impact. 

"Rosetta has entered the history books once again," said Johann-Dietrich Worner, ESA's Director General. 

"Today we celebrate the success of a game-changing mission, one that has surpassed all our dreams and expectations, and one that continues ESA's legacy of ‘firsts' at comets," Worner noted in the statement released on Friday.

Since launch in 2004, Rosetta's nearly eight billion-kilometre journey included three Earth flybys and one at Mars, and two asteroid encounters.

The craft endured 31 months in deep-space hibernation on the most distant leg of its journey, before waking up in January 2014 and finally arriving at the comet in August 2014.

After becoming the first spacecraft to orbit a comet, and the first to deploy a lander, Philae, in November 2014, Rosetta continued to monitor the comet's evolution during their closest approach to the sun and beyond.

The decision to end the mission was due to the spacecraft's ever-increasing distance from the sun, which has resulted in significantly reduced solar power with which to operate the vehicle and its instruments.

Mission operators were also faced with an imminent month-long period when the sun is close to the line-of-sight between the Earth and Rosetta, meaning communications with the craft would have become increasingly more difficult.

"With the decision to take Rosetta down to the comet's surface, we boosted the scientific return of the mission through this last, once-in-a-lifetime operation," Mission Manager Patrick Martin said.

Many surprising discoveries have already been made during the mission, not least the curious shape of the comet that became apparent during Rosetta's approach in July and August 2014. 

Scientists now believe that the comet's two lobes formed independently, joining in a low-speed collision in the early days of the Solar System.

Long-term monitoring has also shown just how important the comet's shape is in influencing its seasons, in moving dust across its surface, and in explaining the variations measured in the density and composition of the coma, the comet's "atmosphere".

Some of the most unexpected and important results are linked to the gases streaming from the comet's nucleus, including the discovery of molecular oxygen and nitrogen, and water with a different "flavour" to that in Earth's oceans.

Together, these results point to the comet being born in a very cold region of the protoplanetary nebula when the solar system was still forming more than 4.5 billion years ago.

Rosetta was an ESA mission with contributions from its member states and NASA.

(With IANS inputs)