Philae lander delivers 'ground truth' by touching and analysing material on a comet's surface

Rosetta's lander Philae. Photo: PA

Do you remember where you were on November 12, 2014 when Philae landed on comet 67P/Churyumov-Gerasimenko?

For three nerve-wracking days, the world's attention was focused on the tiny spacecraft, as it bounced its way across the surface of the comet, 300 million miles from Earth.

Though it landed in the wrong place, Philae managed to carry out a set of of scientific measurements before its batteries ran out and the orbiting Rosetta spacecraft lost contact.

The world mourned the loss of their adopted plucky lander.

Rosetta Mission head Paolo Ferri behind a model of the Philae lander. Credit: Reuters

Today, the fruits of that flurry of activity in November are published in the journal Science.

In a series of seven research papers, scientists from across Europe have released their analysis of the precious data from Philae and found plenty to get excited about in their understanding of comets.

Until now, almost everything we knew about comets was from distant observations of them.

Philae has now given us "ground truth" by touching and analysing the material on the surface.

Comets such as 67P/Churyumov-Gerasimenko, which normally sit at the edge of the Solar System, are the leftover material from the formation of the planets and, as such, are frozen time capsules into the ingredients and conditions that made our planets.

Philae delivers 'ground truth' by touching comet surface. Credit: European Space Agency

Locked within them are clues to how our planet formed and where some of its basic ingredients - such as water and the molecular building blocks of life - came from.

Today's results are, therefore, important insights into the very earliest years of our Earth.

They also explain why Philae had trouble getting to grips with the comet in its first few hours of contact.

Scientists had to search for the lander. Credit: Rosetta

Scientists now know that the comet's surface at the intended landing site was much softer than they had expected, which might explain why the lander bounced off.

Philae eventually came to rest on a much harder surface many kilometres away, possibly explaining why only one leg was able to anchor to the surface (and only partially in any case).

Lander control Centre in Cologne. Credit: Rosetta.

The Cosac and Ptolemy instruments, meanwhile, collected particles from the surface comet and also from the dust clouds kicked up as the lander bounced its way across.

They identified many organic compounds, some of which have never been seen before on the surface of a comet.

Organic molecules are those made from chains of carbon atoms plus others including hydrogen, oxygen and nitrogen.

Particles were collected from the comet's surface. Credit: PA

They are similar to the ingredients you need to build the components of life, such as proteins, and some scientists believe that comets might have brought these important chemicals to the Earth early in its history.

By firing radio waves through the comet, from Philae to the orbiting Rosetta spacecraft, scientists also know that around 75-85% of comet 67P is empty space.

That isn't in the form of caves but just the space between the individual grains of dust and ice in the body. Whatever 67P is made from, it very loosely packed.

Philae before it touched down on the comet. Credit: ESA

Philae got back in touch with Rosetta on June 13 and it got scientists excited that perhaps the lander could carry out more experiments on the surface of 67P and tell them even more about the origins of our planets.

But, despite a brief series of hellos over the following 10 days in June and a brief message in early July, the lander has been quiet.

As comet 67P moves closer to the Sun, heating up and spewing out more dust and gas, it will be harder for Rosetta to get into the right position to listen out for Philae.

A jagged cliff on the surface of the distant comet. Credit: ESA

No doubt those scientists with instruments on board Philae will keep hoping for more contact after August 13, when the comet gets to its closest approach to the Sun, for just one more set of experiments on the surface.

But, even if that doesn't happen and Philae doesn't send back any more data, they can't be disappointed with what the plucky lander has taught them already.