# 5 Pulling the evidence together

We now know that there are no civilisations on Mars. But we have found evidence for past water. Throughout this course, you have learned about the many different lines of evidence that have been identified to show that Mars was once present on the martian surface in significant quantities: rivers, lake beds, and maybe even an ocean may have been present 4 billion years ago.

- What evidence can you list that indicates that water was once present in Mars’ ancient past?

- The evidence for a wet ancient Mars is extensive and has come from orbital and rover/lander investigations and the study of martian meteorites. Some things you might have noted are:

  - Geomorphological evidence – gullies, river channels, streams
  - Geological evidence – sedimentary rocks such as conglomerates and mudstones, ‘blueberries’, cross bedding, horizontal bedding,
  - Mineralogical evidence – clay minerals, sulfates, carbonates, iron oxides, silica

  There has also been direct measurement of water in martian meteorites.

On the basis of this evidence, researchers have been able to recreate the watery environments of some parts of Mars, and their relevance to the potential for life to have once existed.

Mars today, though, is dry and hostile, with a very, very thin atmosphere and ExoMars has shown us that water vapour can be lost to space. However, some water does still exist on the planet.

- List the evidence to support the suggestion that water is present today on Mars.

- Again, evidence has come from orbit and from rovers/landers on the surface. You might have listed:

  - The detection of water in the soil
  - Water frost seen on the martian surface
  - Water-ice clouds
  - Water vapour detected in the atmosphere
  - Hydrogen (indicating water) and water itself detected at the poles and across the planet’s surface.
  - A subglacial lake in the South Polar Region
  - Subsurface ice

Future missions may be able to utilise this water – for life support, fuels or other purposes – to enable humans to walk on the planet’s surface. But it’s imperative that those environments are understood first, to prevent any unintended harm from coming to life that may inhabit those places.

OpenLearn - The search for water on Mars
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