The Mars Global Surveyor probe in orbit around Mars. Image: NASA/JPL.

A storm of shooting stars has, for the first time, been detected in the Martian atmosphere by a team of scientists based at the Armagh Observatory.

The data was taken from the Mars Global Surveyor (MGS) satellite, which has been orbiting Mars since 1997, and is derived from the tell-tale signatures that meteor showers leave imprinted in the Martian atmosphere. "When meteors burn up in the atmosphere the metals contained within them are ionised by sunlight to form a layer of plasma," explains Dr Apostolos Christou, who presented the results at the National Astronomy Meeting on Wednesday. "This happens at an altitude of about 80-95 kilometres for Mars, and although the metallic ions cannot be observed directly by the MGS instruments, evidence for the plasma layer is inferred by monitoring the electron density in the atmosphere."

Christou and his colleagues have developed a model to predict meteor showers caused by the intersection of Mars with dust trails from comet 79P/du Toit-Hartley. From the model, the team identified six predicted meteor showers, for which data was analysed for two showers in April 2003 and March 2005.

For the 2003 dataset the team found that the ionospheric disturbances appeared at the exact time of the meteor shower and in the predicted location. "It's difficult for the observations to be correlated to anything else," says Christou. "The ionisation patterns live for a few hours corresponding to the time of the meteor shower. It was also at the right altitude and it happened on the hemisphere of Mars that was facing the shower at the time."

The 2005 dataset, however, yielded no features indicative of a meteor shower. "We speculate that the meteors in this case were larger than the 2003 outburst, maybe 5 millimetres in diameter compared to 1 millimetre, and so they burnt up deeper in the Martian atmosphere where their ionisation effects were less efficient, so the signatures could not be observed."

What is evident is that more data is required to understand exactly how the ionosphere reacts to meteor influx. The team hope to test their predictions further when comet 79P intersects Mars' orbit again in 2010, 2014, 2016 and 2024. There are also plans to investigate the possibility of making observations with Europe's ExoMars mission, which is due to land on Mars in 2015.

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