Comet chemistry

The galaxy, which is studied by atmospheric and planetary chemists

ESA’s Rosetta mission and a close encounter with Mars

Impact summary

On Wednesday November 12, 2014 the ESA’s Rosetta mission succeeded in pulling off one of the most ambitious manoeuvres in space exploration: soft-landing a robotic probe on a comet for the first time.

Comet 67P/Churyumov–Gerasimenko had travelled from the outer-most region of the Solar System to about 580 million km from Earth (about halfway between the orbits of Mars and Jupiter).

The mission could bring ground-breaking discoveries, as comets are a likely source of the Earth's oceans, as well as a source of compounds such as amino acids – the ‘building blocks of life’.

Professor John Plane said: “We know that comets produce organic molecules, such as amino acids and peptides. The big question is whether they formed inside the nucleus of the comet and then evaporated, or formed through photochemical reactions on dust in the tail.

"If the former, then these relatively fragile molecules could have survived entry to the Earth’s atmosphere inside comets that made glancing impacts. 

“If the latter, they would probably have been destroyed as shooting stars on entry.

“The really big result will be if Rosetta’s landing probe, which is called Philae, detects ‘chiral amino acids’ – amino acid molecules of identical composition but mirror images of each other – of which only one chiral form is found in biological systems on Earth."

Comet ‘flyby’ disturbs Martian atmosphere

Professor Plane was also involved in research presented at a NASA press conference about the MAVEN probe that is currently in orbit around Mars.

A “once-in-a-lifetime” chance to watch a comet flying close to Mars gave a unique insight into the effect of such a near miss on a planet’s atmosphere. 

The comet (C/2013 A1 Siding Spring’s) travelled within about 87,000 miles of Mars, less than half the distance between Earth and the Moon and more than ten times closer than any comet is known to have come to our planet.

This flyby encounter was watched by NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft on October 19, which by amazingly good luck was in the right place at the right time.

Professor Plane collaborated in the analysis and interpretation of the observations carried out by the MAVEN, NASA’s Mars Reconnaissance Orbiter (MRO), and a radar instrument on the European Space Agency's (ESA’s) Mars Express spacecraft, which revealed that debris from the comet added a temporary and very strong layer of ions to the ionosphere, the electrically charged layer high above Mars.

Professor Plane was asked to advise the MAVEN mission on what the likely effects of the flyby would be and what the orbiter’s Imaging UV Spectrometer (IUVs) should be looking for. 

He modelled the amount of metals such as iron and magnesium that would be injected into the Red Planet’s upper atmosphere and what emissions could be expected.

The research was done by Professor John Plane of our Atmospheric and Planetary Chemistry research group, in collaboration with the European Space Agency (ESA).