Rosetta’s Mission Ends with Controlled Comet Impact

Confirmation of the end of the European Space Agency’s (ESA) Rosetta mission arrived at the ESA control centre in Darmstadt, Germany on September 30 at 11:19 UTC (13:19 EST) with the loss of Rosetta's signal upon impact.

Rosetta carried out its final manoeuvre at 20:50 UTC (22:50 EST), setting it on a collision course with the comet from an altitude of about 19 km (11.8mi). 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 Earth before the impact. It is now no longer possible to communicate with the spacecraft.

Sequence of images captured by Rosetta during its descent to the surface of Comet 67P/C-G on 30 September. (Image courtesy of ESA/Rosetta/MPS.)

"Thanks to a huge international, decades-long endeavour, we have achieved our mission to take a world-class science laboratory to a comet to study its evolution over time, something that no other comet-chasing mission has attempted," said Alvaro Giménez, ESA's director of science.

"Rosetta was on the drawing board even before ESA's first deep-space mission, Giotto, had taken the first image of a comet nucleus as it flew past Halley in 1986,” Giménez added. “The mission has spanned entire careers, and the data returned will keep generations of scientists busy for decades to come."

Concluding the Rosetta Mission

Since launch in 2004, Rosetta is now in its sixth orbit around the Sun. Its nearly 8 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.

Rosetta's OSIRIS narrow-angle camera captured this image of Comet 67P/Churyumov-Gerasimenko at 06:53 UTC from an altitude of about 8.9 km during the spacecraft's final descent on 30 September. The image scale is about 17 cm/pixel and the image measures about 350 m across. The image shows a portion of the small comet lobe, with portion of the rough Hathor region (top right) and smoother Ma'at (bottom left). (Image courtesy of ESA/Rosetta/MPS.)

The decision to end the mission on the surface is a result of Rosetta and the comet heading out beyond the orbit of Jupiter again. Further from the Sun than Rosetta has ever journeyed before, there would be little power to operate the craft.

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

Insights from the Rosetta Mission

While the operational side of the mission has finished today, the science analysis will continue for many years to come.

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's planned impact point in Ma'at shown in context with Philae's first and final touchdown sites. All three sites are on the smaller of Comet 67P/Churyumov-Gerasimenko's two lobes. Insets show close-up details of the three sites. Philae's first touchdown in Agilkia was captured by the lander's descent camera ROLIS; the image shown here was taken from a height of just 9 m above the surface on 12 November 2014, and has a resolution of 0.95 cm/pixel. The view at Philae's final touchdown site, known as Abydos, was taken by the lander's CIVA camera on 13 November 2014; the image shown here is a two-image mosaic, and includes one of the lander's feet. (Image courtesy of ESA/Rosetta/Philae/CIVA.)

While it seems that the impact of comets like Rosetta's may not have delivered as much of Earth's water as previously thought, another much anticipated question was whether they could have brought ingredients regarded as crucial for the origin of life.

Rosetta did not disappoint, detecting the amino acid glycine, which is commonly found in proteins, and phosphorus, a key component of DNA and cell membranes. Numerous organic compounds were also detected by Rosetta from orbit, and also by Philae in situ on the surface.

Overall, the results delivered by Rosetta so far paint comets as ancient leftovers of early Solar System formation, rather than fragments of collisions between larger bodies later on, giving an unparalleled insight into what the building blocks of the planets may have looked like 4.6 billion years ago.

"Just as the Rosetta Stone after which this mission was named was pivotal in understanding ancient language and history, the vast treasure trove of Rosetta spacecraft data is changing our view on how comets and the Solar System formed," said project scientist Matt Taylor.

"Inevitably, we now have new mysteries to solve. The comet hasn't given up all of its secrets yet, and there are sure to be many surprises hidden in this incredible archive. So don't go anywhere yet – we're only just beginning."

For more on this historic mission, Rosetta’s manager tells us how to land on a comet.