Professor Monica Grady CBE, best known for her enthusiastic reaction when the Philae lander touched down on comet 67P/Churyumov-Gerasimenko, joins us as part of the Nottingham Trent University distinguished lecture series to talk about the Rosetta mission...
Why go to a comet? They are made from the earliest material that comprises the solar system – in fact, comet 67P is 4.6 billion years old. Most comets are found in the Oort cloud, the extent to which the sun's gravity exerts its influence. The long-period comets live here and contain most of the water and ice within the solar system. When Earth formed, it was completely molten. Over time, it cooled and was hit by several comets and asteroids – this is where all Earth's water came from. By examining comets, we can try and work out how much of the Earth's water came from comets and what other kinds of organic compounds are also found on comets, which may also have been brought to Earth.
The Rosetta stone is from 196BCE and contains the words of a decree from Ptolemy V in Greek, demotic script and Egyptian hieroglyphics. It allowed translation of the hieroglyphics and hence understanding of Egyptian culture – it opened our eyes to the history of all human culture. This is why Rosetta was an apt name for the mission – it was hoping to open ours eyes to the very beginnings of humanity. The lander Philae was named after a place in Egypt that is noted for its temple. The obelisks there helped with translating the Rosetta stone – they helped to illuminate it.
The mission launched in March 2004. It should have launched a year earlier but was delayed due to issues with the Ariane rocket. When the mission was delayed, a new comet had to be found – one that was the right size, travelling at the right speed, on the right trajectory. Very few comets fitted this description, but comet 67P, which was first discovered in the sixties by Churyumov and Gerasimenko, was one that did. In June 2011, Rosetta went into hibernation to be re-awoken in January 2014.
In August of that year, it caught up with the comet, matched its speed, and in November 2014 Philae was launched. After seven hours, it finally landed on the comet. The mission finally ended in September 2016 when Rosetta made a controlled landing on 67P. The mission was first designed in the eighties, and the instruments had to be delivered in 2001. Since they had taken around three years to build, this was comparatively ancient technology. To put that into perspective, just imagine how far mobile phone technology has come since 1998.
When the first proper image of the comet came back, it did not match the shape everyone had expected – it looked like a duck rather than a potato. Initially, this put off the engineers on the mission, they didn’t want to land on the comet. They came up with a solution but then further images showed that the comet wasn't as smooth as they'd hoped. It really didn't look like a comet and the engineers started grumbling again.
Eventually a landing spot was identified, and a competition was held to name it. Monica, along with 200 other people, suggested Agilkia. This is the name of the place that the Philae temple was moved to. UNESCO had to move the temple brick by brick when it started to flood after the building of the Assam dams.
While Professor Grady didn't show the news footage of her celebrating Philae's landing, we did learn that she had received a text proclaiming her the most embarrassing aunt ever. We also learned that while she embraced her husband Ian Wright, who had designed one of the instruments on Philae (a mass spectrometer the size of a cotton reel that fits into a box the size of a shoe box, which goes into a lander the size of a fridge), he told her to keep smiling as "everything's buggered". This referred to the fact that Philae had bounced – a thruster on top of the lander had failed to fire and then the harpoons didn't fire either. So after all that time spent choosing a landing spot, it didn't go to plan.
The problem was that where it has come to rest, Philae couldn't get any power from the sun. This meant that the lander would only have seventy hours of battery power. However, it still managed to perform 86% of the experiments that it was designed to do. Most of the experiments it couldn't do were due to the lander being on its side so it couldn't use its drill. This meant that the mass spectrometer could only test gasses. No ammonia or ammonium was discovered, but there were some sugars detected that are the building blocks for DNA.
Finally, we see that comets really don't look how they are depicted. For one, they are nowhere near as bright. The relative albedo (how much sunlight is reflected) is just 6%. Compare that to the moon (12%), the Earth (35%) or Enceladus, one of Saturn's moons (99%) There are also questions still to be answered around what causes the landscapes on comets. On Earth, we would know how such things are created, but there is no running water on comets so was it caused by continual freezing and thawing?
The distinguished lecture series returns to the Newton Building on the NTU City Campus, Wednesday 22 February 2017, 6pm, where the Rt Hon Alan Milburn will be speaking on "Mind The Gap: How To Make Britain Socially Mobile"
Nottingham Trent University Distinguished Lecture Series website