Figure 1: The Andromeda Galaxy©John Lanoue

When galaxies collide
The unusual structure of the Andromeda Galaxy, also known as M31 has long puzzled scientists (for those of you requiring directions - it's not a motorway; it's the closest spiral galaxy to the Milky Way). For decades it was regarded as showing little evidence of a violent history (weapons inspectors found nothing), however, recent research conducted by David Block from the University of Witwatersrand shows that M31 was involved in a head-on collision with another galaxy. Forget war of the worlds - this is war of the galaxies. M31 has a spiral galaxy shape but with a couple of interesting additions; two dust rings surrounding it. In a similar way to the ripples produced around the impact site when you throw a stone into a pond, these rings are evidence of an impact. Prime suspect is the nearby dwarf galaxy, M32 and research indicates the impact took place around 210 million years ago. Head-on collisions between galaxies may have been common in the early universe but only a few are known nearby. Having discovered that one took place in our neighbourhood (universally speaking) means scientists can study it in a lot more detail than those further away.

The dark side
Amazing what you can discover with a hardcore telescope and some brains, which brings me nicely on to the next bit - the part the telescopes don't show you. Gerry Gilmore from the University of Cambridge is an expert in dark matter (no, its not found at the bottom of a post-Glastonbury puddle) its actually…well I can't really say because no-one truly knows. Dark matter is unseen matter in the universe, known to exist because of its gravitational pull on other things. Galaxies rotate so something is providing a gravitational pull on the stars otherwise they'd fly apart, but "it" doesn't give off light or radiation. So we don't know what it is, but we do know what it isn't: it isn't stars (because they're not invisible), nor is it a gas (this would have been detected by radio or ultraviolet telescopes). Light from distant galaxies shines right through it, so its not dust either. It could be weird atomic or nuclear particles - a kind not yet seen on earth (how cool is that?) or enormous numbers of cold planets or black holes. Also, its not a local problem nor a small one - missing mass affects the whole universe. We can only see about 10% of stuff in space, and the remaining 90% is dark matter. Gerry's latest research has resulted in 3-D maps of galaxies where the impression of dark matter has been traced using thousands of measurements of the gravitational movement of the stars. This volume detection has allowed the mass of the matter to be measured and the temperature also. This is big news because they're the first things to be discovered about Dark Matter other than the fact it exists. This will have massive implications on future studies and the way scientists view the universe, not least because it shows that our galaxy, the Milky Way, is much huger than previously thought and much bigger than neighbouring Andromeda which until recently was thought to be the larger of the two.

Life on Mars Jan Peter Muller from the Mullard Space Science Laboratory is a member of the Life on Mars mission. His work uses new images of Mars from the High Resolution Stereo Camera (HRSC) onboard the European Space Agency spacecraft 'Mars Express', which is currently in orbit. The overall goal is to investigate possible habitats for life, and to understand the recent climate history of Mars. In order to work out what the atmosphere was like in the past, the team is searching for evidence recorded in the surface geology of Mars (particularly the geology of landforms associated with water or ice). They are working on new ways to process and analyse spacecraft data using cutting-edge photogrammetry and computer vision techniques to retrieve unique 3D information and automatically detect surface geological structures such as craters. These aspects are essential for getting the most out of the images of the Martian surface and involve three aims -

1) Determining the origin, age, volume, source and history of the newly-discovered equatorial frozen seas and ice sheets of Mars using geological interpretation of the HRSC data. Importantly, not just use traditional black and white spacecraft images but also 3-D topography maps obtained using the HRSC's stereo imaging capabilities.

2) Developing a state-of-the-art Digital Photogrammetric processing system, including digital terrain model (DTM) creation and automated crater detection to provide the finest resolution and best quality DTMs. This allows the registration of Mars pictures exactly over the shape of the terrain, essential for accurate geological studies. Part of this work was to combine 2D images together to create a 3D version of Mars (similar to Google Earth in the way that you can swoop down between the
mountains and gullies). Interestingly, the resolution is so good that we now know the surface of Mars in more detail than the surface of Earth!

3) Studying river-like networks in ancient Martian terrain. This is undertaken by looking at the interactions between the patterns of the channels, the boundaries between different 'catchment' areas, and the ages of the terrains to assess the role of liquid water at the Martian surface.

See www.google.com/mars/ for some great aerial pictures and www.life-on-mars.org for further details of the project.

To hear more about galaxy collisions, the discovery of the properties dark matter and the search for life on Mars tune in this Sunday to the famous Naked Scientists Radio Show.