Comet landing holds key to origins of life on Earth

Apart from his family, scientist Matt Taylor is obsessed with two things: Tattoos and comets.

The Philae lander at work on Comet 67P/Churyumov-Gerasimenko, as scientists attempt to make history this week by landing a robotic probe on the surface of a comet more than 500m kilometres away.  

His torso — inked from stem to stern — is a shrine to his first obsession. He wouldn’t look out of place at a heavy metal concert as, in looks at least, he is no Albert Einstein.

His work with the European Space Agency’s rendezvous with Comet 67P/Churyumov-Gerasimenko is testimony to his second.

The bricklayer’s son from London is one of two men in charge of the science being done by the European Space Agency’s Rosetta mission to land on the comet and hopefully extract secrets about how life began on Earth.

The other is Irish scientist Laurence O’Rourke, a graduate in microelectronics from University College Cork, who describes Rosetta as a ‘flying laboratory’. Scientists believe comets brought most of the water to Earth, laced with carbon molecules that transformed into primordial life.

A successful landing will allow Rosetta to examine closely the molecules on the comet.

Early last month activity in the region above the ‘neck’ of the comet became high enough for water and carbon dioxide to be detected.

This is perhaps mankind’s greatest space adventure — a feat of engineering many times more complex than the moon landings. The challenge, begun on lift-off in French Guiana10 years ago, was to catch a speeding bullet and land on it.

Getting there wasn’t easy, as the spacecraft had to use gravity to gather enough speed to catch up with the comet. Rosetta became a sling-shot, circling the sun three times, negotiating the asteroid belt twice and gaining speed with each gravitational kick from fly-bys of Earth and Mars.

That landing isn’t a walk in the park, either, and will be made by Rosetta’s Philae lander, a device that looks like a spider with legs to land on the comet’s surface. Touchdown is due to take place on Wednesday at around 4pm Irish time.

It’s not just about getting there, though. The real mission involves gathering data from the comet’s nucleus, coma, and fiery tail, to help us answer the big question: Where do we come from? This is a unique opportunity to bring back original data from an object that has been hurtling through space for billions of years.

“The comet is a time capsule,” explains O’Rourke, who is based at the ESA astronomy centre near Madrid in Spain. He is part of a team of 25 people of 12 different nationalities who will oversee the operation of the 11 laboratory instruments on board Rosetta. “It is a big team but this is a mission that inspires everyone involved in it,” he says.

O’Rourke is also the ESA system engineer for the landing and is now at the lander control centre in Cologne in Germany to prepare for touchdown.

The Rosetta mission is the first to give scientists a close-up view of a comet as it transforms from a cold, dirty snowball to an active body that sheds dust and gas as it swings around the sun.

ESA’s director general, Jean-Jacques Dordain, could hardly contain his excitement as the spacecraft hovered over the comet. “Europe’s Rosetta is now the first spacecraft in history to rendezvous with a comet, a major highlight in exploring our origins,” he says. “Discoveries can start.”

They already have, since last May when Churyumov-Gerasimenko — otherwise known as the Rubber- Duck comet — woke from its long sleep in deep space as it grew nearer the sun.

In July, Rosetta caught up with the comet more than 400m kilometres from Earth as it streaked towards the sun at around 55,000km per hour.

As soon as Rosetta came into closer contact with the comet, ESA scientists were able to begin gathering data, first by using the onboard Visible and InfraRed Thermal Imaging Spectrometer. The data it fed back to Earth took scientists by surprise.

“It was different to what we expected,” says Taylor, explaining that its odd shape and temperature was not what they anticipated but saying that the choice of comet was fortuitous.

“It has features and characteristics of all the comets we have looked at before, so we made a good choice.”

Since July, VIRTIS has been measuring the average temperature of the comet’s surface, finding it to be around –70°C at the moment.

“As we got closer to the comet, we were able to use different instruments and examine it in different wavelengths,” Taylor explains. “Infrared imaging showed the comet to be warmer than we expected and it was more of a dusty surface than an icy surface.”

As it has grown closer to the comet, more instruments have begun to gather data. Scientists have even examined what the comet tastes and smells like.

“This helps to give us an idea of where the comet has come from and linking it to the origin and evolution of the solar system,” Taylor told a multinational online ‘hangout’ of scientists and geeks last Friday.

“The key thing here is that it is not the perfume that some of us would choose to wear,” he told them. “It’s a bit smelly. It’s a bit methaney, a bit rotten-eggy, but at least there’s some alcohol, which some of us might enjoy.”

Two Irish companies are playing a central role in the mission. The design, construction and testing of the electrical support system for Rosetta was done by Susan McKenna Lawlor, a professor at NUI Maynooth, who heads Space Technology Ireland which is based on campus.

The system is considered to be ‘mission critical hardware’ as it is required to handle the communications between the spacecraft and the 11 experiments aboard the Lander Philae on the comet’s surface. Another Irish firm, CAPTEC, based in Malahide, Co Dublin, wrote the software that lets Rosetta communicate with the smaller Philae probe on the surface.

On Wednesday, Rosetta will try to place Philae on the surface of the comet. On touchdown, it must attach itself to the icy surface or it will bounce off into deep space. Using harpoons, it must attach to its nucleus, which is travelling through space at 20km per second.

“We have chosen a landing site at the head of the comet,” O’Rourke says. “On Wednesday morning we will begin firing rockets to change direction towards the comet. Then we separate the lander, allowing it to free-fall to the surface.”

The mission will continue afterwards, circling the sun and relaying data for about the next two years.

O’Rourke says of Rosetta: “I have worked on five satellite missions but this stands out as the most unique.”

Taylor is more visual in his attachment to Rosetta. He had a tattoo dedicated to the mission put on his right thigh after the spacecraft woke from hibernation last January. If all goes well with the landing, there may be a little more inking to be done.

Comet facts

-Comet 67P/Churyumov-Gerasimenko is a 4km-wide sooty lump of ice and dust weighing 10bn tonnes. Yet it has the density of pinewood — if dropped into an ocean it would float. Because of its odd shape, it has been described as looking like a rubber duck.

-Philae is scheduled to land on the comet at around 3.30pm, UK time. It will be the first man-made object to touch down gently on a comet, travelling at walking-pace. In 2005, the US space agency Nasa’s Deep Impact mission smashed a projectile into comet Tempel 1 to study the debris thrown up

-The comet is 509m kilometres away — so far that it will take 30 minutes for the radio signal confirming a successful landing to reach Earth.

-Philae will be deployed from its mother ship at 8.35am, Irish time. During the seven-hour descent, it will take images, sample dust and conduct scientific experiments. To make sure Philae is on target, Rosetta will first “dive-bomb” the comet before ejecting the robot from a distance of 22.5 kilometres and veering off onto a trajectory that will permit permanent radio contact with the probe.

-The landing site, originally known simply as ‘Site J’, has now been named Agilka, after an island on the Nile river in southern Egypt. It was chosen because it is a relatively flat region on the comet’s rugged surface, which is covered in boulders, jagged outcrops and steep cliffs.

-Philae takes its name from another Nile island, where an inscribed obelisk was discovered that helped Egyptologists break the Rosetta Stone code. Ancient buildings, including the famous Temple of Isis, were moved from Philae to Agilka when their original home was flooded during the building of the Aswan dams in the last century.

-As it touches down, two harpoons will anchor Philae to the comet’s surface to prevent it bouncing off and back into space. Whirling ice screws attached to the probe’s three legs will also fasten themselves into the comet’s crust.

-Scientists are still not entirely sure what the surface of the comet is like. Too soft, and Philae could sink. Too hard, and it could rebound away into space. Philae’s box-like outer casing is covered in solar cells to capture energy sunlight. Measuring a metre across, it is about the size of a dishwasher

-The robot carries a suite of 10 scientific instrument packages designed to capture a plethora of data about the comet, including its magnetic field, temperature, radiation levels and composition. Sensors on its legs will even test how sound travels through the surface. Several cameras will take panoramic and close-up pictures.

-Philae also has a drill that can bore out samples to a depth of 23cm. The samples will be heated and turned into gas for analysis in the probe’s on-board laboratory.

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