Mullard Space Science Laboratory

P R E S S  R E L E A S E

24 February 2004
REF: MEX2004-2

Europe goes to Mars.
Mars Express: Europe's first solo space mission to another planet

Europe's first solo space mission to another planet is now in orbit around Mars. The red planet was once warm and wet, but is now dry and barren. At present, liquid water would immediately evaporate in the cold, low pressure surface conditions. One of the key questions about Mars is where did all the water go. Now, Mars Express is sending back information about the story of water on Mars, from under the surface, through the atmosphere and escaping to space.

Images from earlier orbiting spacecraft reveal that Mars has ancient river channels at least 3.8 billion years old. During this warmer, wetter period, Mars also had a magnetic field. Since this was lost, Mars has been losing atmosphere at a rate thought to be up to 100 tonnes per day, as the solar wind tugs away at the upper atmosphere. Over 3.8 billion years, this adds up to a lot of atmosphere lost to space.

UCL-MSSL are involved in the Aspera instrument which is measuring the rate of atmospheric loss more accurately and completely than ever before. Dr Andrew Coates, a co-investigator on Aspera, says 'Mars behaves like a weak comet with an invisible tail. At comets, the tails are due to escaping gas and dust. What Aspera will do at Mars is to measure the gas escape rate accurately, this will help us find what Mars' atmospheric pressure was at the end of the warm-wet period. This is important because we want to understand whether conditions could have been right for life at this time.'

Aspera, a Swedish-led instrument, is working well and has already measured oxygen, from water, escaping along the tail. Also the US-built electron spectrometer, for which MSSL provided blackening and calibration technology, has made its first measurements of Mars' poorly understood plasma environment. The results look very promising. 'With Mars Express we can see details of the process which makes Mars lose its atmosphere and how it interacts with the solar wind. As results build up we expect to gather a complete picture which will reveal how much of the Mars atmosphere has been lost to space over billions of years'.

Notes to Editors

1. The Mullard Space Science Laboratory, situated at Holmbury St Mary, is the Department of Space and Climate Physics of University College London. About 120 people work on space science and space engineering. The Laboratory plays key roles in many missions of space exploration. Over 250 instruments have been launched into space to date, to study astrophysics, solar and stellar physics, plasma and planetary physics and climate physics.

2. Mars Express is a mission of the European Space Agency's Science Programme

3. The Aspera team is led by the Institute for Space Physics in Sweden; the electron spectrometer was built by SwRI in Texas



Mullard Space Science Laboratory
University College London
Holmbury St. Mary, Dorking
Surrey, RH5 6NT

MSSL switchboard: 01483 204100
MSSL website:

Dr Andrew Coates: 01483 204145