Water is essential for life on Earth – Considered the source of all life. For this reason, many believe that any extraterrestrial life must require water. For scientists, knowing the location of water is crucial if we decide to venture beyond our planet and become an interplanetary species.
Potential Habitats for Life in the Solar System
Fortunately, the search for water is something humanity excels at. Modern science allows astronomers to do this over vast distances and through various obstacles such as murky clouds and miles of ice. Below are seven locations that may contain water in the Solar System.
1. Mars
While the notion that Mars has vast canals filled with water to sustain lush vegetation has been dismissed since the 1920s, scientists believe Mars has a significant amount of water comparable to Lake Superior (the largest and deepest lake in North America’s Great Lakes). Most of this water is frozen in polar ice caps, with a certain amount found in the atmosphere.
Liquid water exists only in small lakes beneath glaciers at the poles. Identified through radar, this lake lies beneath 1.5 km of ice and is thought to be in a liquid state due to the antifreeze properties of certain minerals in Martian soil.
2. Europa – Moon of Jupiter
One of Jupiter’s Galilean moons, Europa, is famous for its solid icy surface and oceans that stretch beneath the moon. The ice crust on this satellite is estimated to be several kilometers thick, potentially reaching up to 30,000 meters.
Europa is known for its solid icy surface and oceans that stretch beneath the moon.
The ocean beneath is believed to be 100 km deep, with some areas potentially being a mixture of sludge above and mostly liquid below. If true, this means Europa has more water than all the oceans on Earth combined, nearly three times as much.
These vast oceans, kept warm by Europa’s volcanic core and the tidal forces exerted by Jupiter, are thought to be an environment that could nurture extraterrestrial life. Hydrothermal vents, similar to those on Earth, could provide energy and conditions for life in an environment that may never see the Sun.
(The Galilean moons are the four largest natural satellites of Jupiter – Io, Europa, Ganymede, and Callisto).
3. Ganymede – Moon of Jupiter
Ganymede is another Galilean moon of Jupiter and the ninth largest object in the Solar System – larger than both Mercury and Pluto. Ganymede is known as the largest moon in the Solar System and the only moon known to have a magnetic field, which indicates the presence of a massive ocean beneath its icy surface.
Ganymede is known as the only moon in the Solar System with a magnetic field.
By observing the movement of Ganymede’s magnetic field, partially caused by its interaction with Jupiter, astronomers have noted subtle changes indicating the existence of a large salty ocean.
This ocean is estimated to lie beneath a thick ice shell of 150 km and could be up to 100 km deep. Like Europa, it may also contain more water than all the oceans on Earth combined.
Recent observations have confirmed the presence of water vapor in Ganymede’s thin atmosphere, possibly due to the evaporation of water ice from the surface of this moon.
4 & 5. Ice Giants: Uranus and Neptune
Uranus and Neptune are referred to as “ice giants” because they are primarily composed of heavier elements than hydrogen and helium, combined with a large amount of water, ammonia, and methane ice.
Uranus and Neptune are referred to as “ice giants”. (Source: Lunar and Planetary Institute).
Unlike gas giants like Jupiter and Saturn [which rely on gas to provide 85% of their mass], ice giants are thought to have supercritical water oceans – that is, water at temperatures and pressures above its so-called critical point, where liquid and gas become indistinguishable. This supercritical water constitutes two-thirds of their total mass.
It remains unclear exactly how they formed, and scientists are planning to investigate further.
6. Titan – Moon of Saturn
Titan, Saturn’s largest and most intriguing moon, is a strange place.
The second-largest moon in the Solar System (after Ganymede), Titan is characterized by an atmosphere rich in nitrogen and substantial amounts of liquid methane, leading to a “methane cycle” unlike the water cycle on Earth – complete with rain, lakes, rivers, and seas at a chilly temperature of -179 °C.
However, even here, there is water. Ice is believed to lie beneath the rocky surface, and liquid water mixed with enough ammonia to prevent it from freezing. This was determined by the Cassini spacecraft, which studied the tidal forces on Titan.
Astronomers believe that there is enough force here to maintain an ocean beneath the surface, likely including water.
