Mercury, the planet closest to the Sun, is a small rocky body that is only 0.45 times bigger than the Moon. We knew very little about Mercury until NASA’s Mariner 10 mission carried out three fly-by observations between 1974-1975, which photographed about 45% of its surface. The mission revealed a planet covered in large impact craters and basins, with plains of lavas infilling many of these craters. The planet also was found to have a magnetic field and large iron core, and a tenuous exosphere.
NASA has recently sent a new mission – called MESSENGER (an acronym of MErcury Surface, Space ENvironment, GEochemistry, and Ranging) – to find out more about Mercury. The mission has been in orbit since 2011 collecting a range of information about the planet’s morphology, topography, composition, mineralogy, magnetosphere and plasma environment. Spectacular new images of the planet’s surface have been sent back showing volcanic vent sites and strange features that are poorly understood known as ‘hollows’.
The MESSENGER mission is changing our understanding of Mercury, and it is an exciting time to be a planetary scientist as views of the planet’s formation and geological evolution are being discussed.
Looking to the future a new mission will be also going to study Mercury in even more detail. The European Space Agency (ESA) and the Japanese Space Agency (JAXA) are sending a joint mission called BepiColumbo, which will launch in ~2015 and get to Mercury in ~2023. The experiments that will fly on the mission are nearly all built, and the UK (led by the University of Leicester) is contributing an instrument package called the Mercury Imaging X-ray Spectrometer (or MIXS for short). This experiment will map the chemistry of the surface of Mercury helping to map compositional variations in different geological features.
I joined other European planetary scientists last week to discuss preparations for investigating the surface and composition of Mercury with the BepiColumbo mission. The working group discussed the changing view of Mercury provided by MESSENGER, and how the different BepiColumbo science teams in Europe can collaborate and work together to maximise the science return from the future BepiColumbo mission. Even if the mission itself won’t get to Mercury for another ten years or so – forward planning and cooperation will be an important path to success.