 Mars, named after the God of War, is our nearest neighbour in the solar system and the planet that has captured our imagination for millennia. Over the last four decades, scientists have sent many space missions to the red planet and even more are planned, but why does Mars get so much attention? Mars is the most similar planet in our solar system to Earth and by studying it we can learn more about our own planet, including whether or not life is possible elsewhere. Researchers have suggested that microorganisms may have evolved on Mars in its ancient past and may even be present today, hidden beneath the surface. We can search for evidence of life on Mars by looking for molecules, minerals and even fossils that organisms leave behind when they die. These indicators of past or present life are known as biosignatures. Mars is one of the best places in our solar system to look for signs of ancient life because of its history. Around four billion years ago, conditions on Mars were much more hospitable than they are today. Since life developed on Earth around this time, is it possible that it also developed on Mars? When deciding if a planetary body could be capable of harboring life, we look for water. Nearly everywhere on Earth where there is water, there is life, which is why we think it is so essential, and there is plenty of evidence to suggest that there used to be liquid water on Mars' surface. Mars has geological features which shows where rivers flowed and impact craters were filled with water, forming huge lakes. It is also thought that the climate was much warmer and the atmosphere was better able to protect the surface from space radiation. But where did the water go? Over Mars' history, it lost its atmosphere, so the planet cooled to the point where the water froze and was unable to exist as a liquid on the surface. On the surface of Mars today, average air temperatures are around minus 60 degrees Celsius. It has a thin atmosphere, meaning that the surface of Mars is not protected from high levels of radiation from space. This makes the surface pretty inhospitable, but scientists think that there is a possibility that microorganisms could survive beneath the surface, protected from the space radiation. It is also possible that traces of microorganisms that lived on Mars in its ancient history may still remain there to be found. Today, water on the surface of Mars exists mainly as ice in the poles. However, some evidence suggests that there may be large reservoirs of water existing underneath the ice at the planet's south pole. Although this is not certain if there is subsurface water on Mars, it would be a huge discovery, as these lakes could be habitats for life. At Astrobiology OU, researchers are looking at different areas of the red planet to understand whether microbes could have survived there. We use images and data from spacecraft and rovers to learn about the Martian surface and atmosphere. Some of our researchers even go to some of the most extreme places on Earth, thought to have similar environments to ancient Mars, to understand more about how microbes could have survived on Mars and whether or not they'd leave behind any signs of their existence. Astrobiology OU works across all the sciences, from microbiology to computer science, to try and answer the question, is life possible on Mars?