Water is usually associated with life. But with life, for the time being, only found on Earth, we sometimes tend to imagine water as a rare commodity. It’s in fact the opposite. Asteroids and comets aside, there is water on every planet in our solar system.
A team of researchers confirmed a few months ago for the first time the presence of water ice at the poles, in the darkest and coldest parts of the lunar surface. So there is plenty of water on our satellite, even though we have known that for many years. But ice, frost or snow are not only found in the Earth-moon system. Water, in whatever form, is omnipresent throughout the solar system. Even in the most unlikely places.
Mercury and Venus
Take for example the case of Mercury, the planet closest to the Sun (about 58 million kilometers, one-third of the distance between the Earth and the Sun). On the diurnal side of Mercury, the temperature sometimes reaches 430 °C. Difficult to imagine the presence of water in these conditions. However, during the 1990s, luminous reflections were noticed in the polar regions. After analysis, it was found that they were the result of the presence of ice water nestled in craters (deposited by meteorites?), a part of which is never exposed to Sun. This would make these craters sufficiently cold (-73 °C) so that the water can remain stable in the form of ice. Researchers now estimate that Mercury could contain between one hundred billion to one trillion tons of water ice.
Another example: that of Venus, the system’s most infernal planet (460 ° C on the surface). On the “twin sister” of Earth, no water ice, but other types of frost and snow. Radar images show us that the highlands of Venus seem surprisingly bright. For researchers, it could be metallic ice, probably composed of lead sulfide and bismuth sulphide. These compounds would be expelled from the surface by volcanic activity, and become vaporized in the atmosphere to finally “freeze” at high altitudes. At 125 kilometers from the surface, the temperature would be -175 °C on Venus.
The red planet….
If we shift a little more outward, and pass the Earth system, we reach Mars. The red planet also carries its weight of water, especially at the poles (water and frozen carbon dioxide). A team of researchers announced a few weeks ago the discovery of a lake about 20 km wide located about 1.5 km under a layer of ice. An incredible discovery that will have to be taken into account during future missions dispatched on site. Could we find microbial life on Mars? Possible. Only the future will tell.
Jupiter, Saturn and their moons
Then come Jupiter and Saturn, which present totally different structures. The two gaseous planets here could contain a lot of ice and snow, probably mixed with ammonia. There is also no solid surface strictly speaking where snow can accumulate. Thus, if there are snowstorms, the flakes could melt at a certain altitude, warmer, and evaporate and then be sent back to a new cycle. The heart of Jupiter could also be a layer of ice surrounding a rocky seed.
There would also be a lot of water in the highest clouds of Saturn. The famous rings of the giant (mainly composed of ice) appear here like gigantic fountains, watering the upper part of the atmosphere of Saturn. But this transfer of ice will only last for a while. New data returned by the probe Cassini revealed indeed a few days ago that the innermost ring (ring C) pours a surprising amount of material in the atmosphere of Saturn: between 432 and 2870 kg each second. The outermost rings then transfer matter to the inner rings – material that eventually falls on Saturn. At this rate, the rings of the planet could disappear in 100 million years.
Water ice in solid form is also present on Enceladus, the moon of Saturn, known for its vast ocean hidden under its frozen shell. Same thing for Europa, the moon of Jupiter. The latter shelters indeed an immense salty ocean, nested under a thick ice crust several kilometers thick, in contact with the rocky core.
According to observations made with the Hubble Space Telescope, an ocean larger than all those of the Earth combined would also be lodged under the thick ice crust of Ganymede, the largest moon of Jupiter. Mars aside, these three frozen moons are now a better chance of one day finding a life “elsewhere” in the Universe.
Uranus, Neptune, Triton or Pluto
Next come Uranus and Neptune, which also show clouds of water ice (as well as ammonia and methane) in their atmosphere. Neptune’s moon, Triton, is also very interesting from this point of view. The passage in 1989 of the Voyager 2 probe made it possible to observe a frozen surface formed mainly of water, but also nitrogen, methane and carbon dioxide. The presence of an underground ocean is also suspected.
As for Pluto, NASA revealed in 2015 the latest images transmitted by the probe New Horizons. These data then allowed us to note, on the one hand that the sky is blue on Pluto, but also that the dwarf planet has plates of ice water on the surface.
Read more: Why Pluto is no longer a planet