Seven signs of water
When astronomers look for liquid water in the Solar System, they focus on seven physical characteristics, which indicate the existence of water in the remote, hostile worlds.
news for astronomers, as it means that a robotic probe needs not force itself down through Europa’s ice crust to find water, it
can be done by a spacecraft.
MARTIAN SOIL AS DRY AS A DESERT
Astronomers are not only looking for water far away in the Solar System, the search has also begun on our neighbouring planet, Mars, but the results are not as good.
According to astronomers, Mars could have been just as wet as Earth some four billion years ago, but the planet’s magnetic field, which protects against radiation from the Sun, is much weaker than Earth’s, and so,
the planet’s atmosphere has become considerably thinner. In 2015, NASA’s MAVEN probe revealed that the constant solar wind particle bombardment removes 100 g of gasses from the atmosphere per second. Hence, Mars could not retain liquid water, and water now only exists in the shape of underground ice.
In the autumn of 2015, NASA proclaimed that scientists had found evidence of salt water flowing down the sides of Martian craters during the summer. The evidence were long, dark lines appearing in the craters in the summer and disappearing in the winter. However, subsequent studies made by the Mars Odyssey probe have shown that the lines hold a maximum of 3 % of water – the same as a desert on Earth. At worst, the lines do not contain any liquid water at all, rather they consist of salts that attract a small quantity of water molecules from the atmosphere.
If so, astronomers need to find out why the lines come and go. A rover such as Curiosity, which is presently roaming Mars, could help, so NASA is considering to send the robot to one of the areas to take a soil sample.
PLUTO SURPRISES ASTRONOMERS
In 2016, yet another surprise came up in the search for liquid water. The dwarf planet of Pluto, which is located on the other side of the Solar System’s most remote planet, Neptune, may include an ocean. The water is freezing, but it may still be liquid.
New images of Pluto taken by the New Horizons spacecraft in 2015 show external, tectonic features revealing that the world has expanded. The expansion could be due to an ocean that is gradually freezing. Based on the new observations, scientists from the US Brown University have been able to update the model of temperature developments on Pluto. If the ocean had already frozen into water ice, it would relatively quickly turn into a special type of densely packed ice due to the high pressure and the low temperatures in Pluto’s interior. That would cause a contraction of the dwarf planet, of which scientists see no signs on the surface. So, the team believes that the water beneath the ice crust may still be liquid.
Space agencies’ search for liquid water does not stop with Pluto. In the 2020s, both NASA and the European Space Agency, ESA, plan to send new craft to Jupiter to take a closer look at the ice moons.
In the long run, cautious fly-bys will, however, not be enough. Instead, craft must land on the surfaces of the worlds. This requires a lot from the measuring equipment that is to function in radiation which is forceful enough to short out the costly gear. If the underground oceans are to be seriously studied, engineers must figure out how to send an unmanned submarine into them, so scientists can find out if the liquid water includes living creatures.