Rosetta comet landing: What’s the big deal?

BY TAI CHISHAKWE - NOVEMBER 13, 2014

The world was on Wednesday overwhelmed by excitement after the Philae lander, which was released from its mothership Rosetta, made a successful and historic landing on comet 67P/Churyumov-Gerasimenko. But if you are not one of the scientists who’ve been working day and night on the Rosetta mission for the last 20 years – or any scientist or space exploration fanatic, should you be excited about the Rosetta space mission?

The answer is an emphatic yes!

Rosetta and Philae travelled more than six billion kilometres – over ten years, to make a successful rendezvous with comet 67P, which orbits our sun at speeds of up to 135 000km/h.

Since comets are believed to be the icy remnants from the formation of our solar system 4.5 billion years ago, it is hoped that the Rosetta mission will unlock more clues about the birth of life on Earth. The mission has already made history by orbiting comet 67P and gathering the most detailed information so far on the composition of the comet’s nucleus.

Here are the exciting facts about this mission.

The first spacecraft ever to land on a comet

The Philae lander is the first spacecraft ever to land on the surface of a speeding comet – which is no doubt a huge achievement in the history of space exploration.

The Rosetta mission will indicate if comets brought water to Earth

It is believed that the water in our oceans and in our bodies originally was deposited on Earth by comets that bombarded the plant during its early formation billions of years ago. The Rosetta mission, it is hoped, will tell us if a barrage of comets did bring water to the infant Earth.

From previous measurements, scientists say that a large proportion of a comet is made of water-ice which turns to vapour as well as microscopic dust when heated by the Sun. So as comet 67P/Churyumov-Gerasimenko approaches the Sun, it will heat up and some of this dust could be ablated to reveal more of the comet’s geology.

Comet 67P/Churyumov-Gerasimenko holds history of solar system from 4.5bn years ago

Scientists believe comet 67P interior contains the initial composition of the solar system from when it was formed 4.5 billion years ago. The results from Philae will help improve models about our solar system and knowledge on how a planet eventually becomes habitable.

Key landing instrument broke on the way down

Philae’s one-shot landing was in itself a great feat because the gravity on comet 67P’s surface is so weak that an astronaut could escape its pull just by jumping.

On touchdown, Philae used two harpoons and icescrews on its three landing legs. The harpoons once fired could not be retracted and re-fired. Fatefully, a thruster on the lander failed on Tuesday night. It was designed to fire when Philae touched the comet preventing it from bouncing off as the harpoons fired.

Without thrusters it also means that there was no chance to change course if a lander-destroying shard of ice and rock is underneath.

Philae needed to land within a one-square-kilometre landing spot

Comet 67P is shaped like a rubber duck with precipices and slopes and a surface pocked with holes and strewn with boulders. When its shape was revealed in July, some thought the landing would never happen.

Several landing sites were ruled out as too dangerous before the European Space Agency settled on a one-square-kilometre landing spot it has named Agilkia. If Philae had strayed outside its landing zone, it had a greater chance of toppling over.

Landing on the right spot meant taking into account the dust and water vapour billowing off the comet and its oddly-shaped gravitational field.

Philae had a less than 75% chance of success

The Philae lander was given a less than 75% chance of success – even after the European Space Agency had spent £1 billion on the Rosetta probe.

Tuesday night’s thruster failure saw that percentage going further down.

“The mission is already a major achievement in space exploration history,” said Andrea Accomazzo, Rosetta flight director, and has worked on the mission for 18 years.

“Exploration implies risk. If you are not ready to take the risk, then you shouldn’t do exploration.”

Read more: Rosetta comet landing: Philae now stable