End of Rosetta probe promises decades of discoveries

As the end of the European Space Agency's Rosetta spacecraft approaches, scientists working with the first probe to rendezvous with a comet insist it will lead to discoveries for decades to come.

As part of its 12-year journey, the Rosetta spacecraft followed Comet 67P/Churyumov-Gerasimenko through the Solar System for two years until it reached the sun and became active on Aug. 6, 2014.

On Nov. 12, 2014, the spacecraft sent the Philae robot lander down to the surface of the comet. Now, the spacecraft is set to say farewell on Friday as it lands on the comet and shuts down.

For the head of Solar System Science Operations Division at the ESA Gerhard Schwehm -- who worked with the Rosetta team from 1985 until he retired as mission manager last March -- this is actually not the end.

In fact, it is the beginning of a whole new stage of research and exploration.

Schwehm evaluates Rosetta's mission as a success which will continue for years to come. He told Anadolu Agency “what's going to happen on Sept. 30 is just the end of the operational phase which concludes with the landing of the spacecraft into the comet".

The mission veteran said Rosetta paved the way to understanding and observing comets. It performed experiments which were never done before.

Comets are considered important in the understanding of the universe since they are believed to be remnants left over from the formation of the Solar System about 4.6 billion years ago.

“The ultimate goal of the Rosetta mission is to find out the composition of the comet and study the material it is made of ... the same material from which our planet Earth was formed 4.6 million years ago ... comets are the most primitive objects that have not changed through the years," Schwehm said.

“We now have a better understanding how a comet works [and] the mobility of the comet," he added.

Rosetta also discovered signs which can prove comets are indeed part of the ancient Solar System, like the oxygen molecules on the halo surrounding the comet – something which has remained a mystery.

Schwehm continued: “The other question that we were seeking to find its answer to is that comets might have brought water to Earth. And the mission confirmed, for now, that comets might have contributed a little bit but not completely.

“And this confirms another theory that asteroids actually brought water to our planet."

Asteroids are relatively small, inactive, rocky bodies orbiting the Sun which were left over from the formation of the planets billions of years ago. They are often known as "minor planets", according to NASA and ESA.

According to the ESA, the decision to end Rosetta's mission was made because the spacecraft had become a piece of floating space debris.

“Combined with an ageing spacecraft and payload that have endured the harsh environment of space for over 12 years -- not least two years' close to a dusty comet -- this means that Rosetta is reaching the end of its natural life and so Sept. 30 was considered the optimum date to conclude the mission," the space agency said in a statement.

The collision maneuver will take place on Thursday evening, initiating the descent from an altitude of about 20 kilometers (12 miles).

Rosetta will essentially free-fall slowly towards the comet in order to maximize the number of scientific measurements which can be collected and returned to Earth before its impact.

As it descends, the spacecraft will be able to take close-up images of the comet and make last-minute gas and dust readings as it gets closer.

“It is not a crash. Just before it impacts the comet it will hit the surface at walking speed," insisted Schwehm.

“The spacecraft will tenderly land on the comet and once it impacts on the surface the spacecraft will switch off all the communication equipment," he said.

The scientist said after dispatching final data to Earth, Rosetta's signal will simply vanish from ground control screens at about 1120 GMT, likely with partly-uploaded data still in the system.

It takes 40 minutes for Rosetta's signal to arrive at mission control in Darmstadt, Germany, meaning the actual time it will be gone forever will be around 1040 GMT.

“Rosetta will collect science data until the very end of its descent on Friday. The opportunity to study a comet at such close proximity makes the descent phase one of the most exciting of the entire mission," ESA added.

Even with over two years' worth of data now safely collected, tracking the comet through its most active period as it passed through perihelion, giving unrivalled insight into its evolution, this is still only the beginning of Rosetta's big discoveries.

“Last month we celebrated two thrilling years since arriving at the comet, and also a year since the comet's closest approach to the Sun along its orbit," Matt Taylor, ESA's Rosetta project scientist said.

“It's hard to believe that Rosetta's incredible 12.5-year odyssey is almost over, and we're planning the final set of science operations, but we are certainly looking forward to focusing on analyzing the reams of data for many decades to come."

Schwehm said the next stage “requires several years of scientific research".

“Rosetta gathered data on its first week more than other similar missions did. Now, scientists from different fields will have to analyze all the massive data collected by Rosetta during the two years," he said, adding : “It will take decades, at least another 10 years, to properly analyze all the data and might potentially open doors to new and more interesting discoveries."

"It is like putting a puzzle together," he added.

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

Its amazing journey lasted 12 years, six months and 28 days from launch on March 2, 2004 to mission end on Friday.