“Is there anyone else out there?”An age-old question that we’ve spent centuries trying to answer, but are still yet to uncover on our little red neighbour Mars.
Despite no signs of life having yet been detected on the red planet, we’ve managed to find quite abit of evidence that suggests liquid water only once flowed on its surface.a) Is there any evidence to prove Mars used to have water?Well Ziyi, there’s actually quite a vast range of evidence that we’ve collected over the years through technologies such as rovers, satellite imaging and petrology techniques. Let’s first look at the evidence from minerals found in the rocks and soil of Mars.1) Hematite: Within weeks of landing on Mars in 2004, NASA’s Rover “Opportunity” discovered hard spheres (as seen in the image 1) scattered across the planet’s surface 1.
It was later demonstrated that the spheres or “blueberries” consisted primarily of the mineral hematite 1 & 2. According to Daniel Rodionov (a rover science team collaborator), “This is the fingerprint of hematite, so we conclude that the major iron-bearing mineral in the berries is hematite” 2.This is a strong indicator that Mars used to have water. This is because on Earth, hematite is generally formed through the oxygen atoms of water binding with iron atoms 3. Hence it has been hypothesised that the “blueberries” were the result of groundwater containing dissolved iron, reacting with sandstone 1. Image 1 Obtained from reference 12) Jarosite: Furthermore, “Opportunity” also discovered the mineral jarosite on the surface of Mars 1 & 4.
Since jarosite is a sulfate mineral that is almost always formed (at least on Earth) in the presence of acidic water 5, this became another discovery that strongly supports the idea that water once existed on the surface of Mars. In the stunning image below that was captured by the High-Resolution Imaging Science Experiment camera, it has been confirmed that the bronze-coloured land on the right is jarosite deposit 6. Image 2 Obtained from reference 6Now, on top of the petrological evidence, let’s also look at the geomorphic evidence of water on Mars.1) Rivers: Not only was Mariner 9 the first spacecraft to orbit Mars in 1971, it was also the first to capture photographs of what appears to be dry river beds and canyons on the red planet’s surface 7. These images (such as image 3) suggest that floods of water once flowed through rivers, carved deep valleys and eroded grooves into bedrock. A comparative analysis of Image 3 and an image of the Mississippi River in America, reveal that the two resemble each other to a conspicuous degree.
This is another compelling piece of evidence that indicates water once flowed on the surface of the red planet. Image 3 Obtained from reference 8 Image 4 Obtained from reference 92. Eridania Lake: Using images produced by the Mars Orbiter Laser Altimeter (as seen in Image 5), scientists have hypothesised that a 1.1 million KM2 lake once existed on Mars 10. To give you an idea of how colossal this lake was, it contained more water than all the other Martian lakes combined and is larger than the Caspian Sea 11.Scientists came up with this hypothesis after observing evidence that the valley and river networks around the lake all ended at the same elevation 11 & 12.So what if they all ended up at the same altitude? How does this suggest a lake?Well if all these valleys ended up at the same level, then this implies that they must’ve all flowed to and emptied out in the same area – namely the Eridania lake.
This theory has been further supported by the fact that scientists have found that seafloor hydrothermal deposits exist where the lake once was 11. These deposits are volcanic sulfide deposits, that are almost always created in large bodies of saltwater; such as large salt lakes and oceans 13. This is another key discovery that supports the claim that the Eridania Lake once was filled with water. Image 5 Obtained from Reference 14Now, although there is other evidence of water on Mars that I haven’t covered – such as weathering rates (which maybe someone else can discuss if they wish to) – I believe that the presence of hematite, jarosite, rivers and lakes are the four most convincing pieces of evidence that our red neighbour once contained liquid water.References