Rosetta: The beginning of the end

The opportunity to study a comet at such close proximity makes the descent phase one of the most exciting of the entire mission.

DARMSTADT, Germany: Europe was poised to send its Rosetta spacecraft yesterday toward a crash landing on the comet it has stalked for the last two years, joining robot lander Philae on the icy dustball’s surface for eternity.

The mission will conclude with a last- gasp spurt of sciencegathering as Rosetta quits the orbit of comet 67P/ChuryumovGerasimenko at about 2050 GMT to start a 14-hour, 19-kilometre (12-mile) descent.

This will all happen more than 700 million kilometres from Earth, with the comet and Rosetta zipping through space at a speed of over 14 kilometres (nine miles) per second.

“Rosetta will collect science data until the very end of its descent,” said the European Space Agency’s Rosetta blog.

“The opportunity to study a comet at such close proximity makes the descent phase one of the most exciting of the entire mission.”

A ‘controlled impact’ is scheduled for about 1040 GMT on Friday, with confirmation of the end of the mission expected some 40 minutes later, which is how long it takes for a signal from Rosetta to reach Earth.

After 12 years in space, Rosetta’s signal will simply vanish from computer screens at mission control in Darmstadt, Germany.

The European Space Agency’s Rosetta blog

The first- ever mission to orbit and land on a comet was approved in 1993 to explore the origins and evolution of our Solar System — of which comets are thought to contain prehistoric elements preserved in a dark space deep freeze.

Rosetta and lander probe Philae blasted off in March 2004, and travelled more than six billion kilometres ( 3.7 billion miles) to reach 67P in August 2014.

Rosetta placed Philae on the comet’s surface in November that year.

Insights gleaned from the 1.4billion- euro ( US$ 1.5- billion) science mission have shown that comets crashing into an early Earth may well have brought amino acids, the building blocks of life.

Comets of 67P’s type, however, certainly did not bring water, scientists have concluded.

Having made the closest approach on its 6.6-year loop in August last year, the comet is moving further and further away from the Sun, which means Rosetta’s solar panels are catching fewer battery-replenishing rays.

Rather than just letting it fade away, scientists opted to end the mission on a high by taking measures from nearer the comet than ever before -- too close to risk under usual operating conditions.

The craft was never designed to land.

On its descent, the plan is for Rosetta to peer into mysterious pits dotting the comet landscape for hints as to what the body’s interior might look like.

“We hope to look at structures on the walls of the pits which may date to the time of the comet’s formation” in the early Solar System, Philae scientist JeanPierre Bibring told AFP.

Rosetta will also take new measurements of 67P’s gas density, surface temperature and gravity field. The closest Rosetta had ever been to the surface was about 1.9 km -- now it will get to take pictures within tens of metres and send them home until just before impact, when it will shut down.

“After Rosetta has touched down, it will not be possible to collect or return any additional data,” the ESA said.

“The unique measurements obtained during this final descent will be a fitting closing chapter to Rosetta’s time spent living with this comet.” — AFP