Every Planet, Dwarf Planet and Moon in the Solar System Known (or hypothesized) to Contain Liquid Water
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| NASA/SSI - via Wikimedia Commons. |
Since humans first began to walk the earth, they have gazed at the heavens in inexorable wonder. We have always wondered if, as we watched the stars above us, someone from those stars was looking back at us. Among the uniquely human qualities are curiosity, wonder and exploration. Our constant search for answers as to whether we are alone is, therefore, no surprise. As our search has broadened, we have begun to see that the water on Earth is not one, but one of many celestial bodies to have liquid water. Even in the solar system, there are many bodies that certainly do or are hypothesized to have liquid water, either on their surface or underground. Let us now explore the other water worlds of our solar system: Mars, Ganymede, Enceladus, Europa, Titan, Callisto, Ceres, Dione, Mimas, and Triton.*
Water means life, right? So far as we know, it does. We search for water worlds exclusively out of our belief that water is an essential indicator of life. Perhaps some of the worlds we explore today could be among the first we find to support extraterrestrial life.
Planets and Dwarf Planets
Mars
Name Origination: named after the Roman god of war, Mars.
Diameter: 4,212 miles.
Surface Gravity: 3.72 N/kg,☨ or about 38% of Earth’s surface gravity (.38g).
Distance From the Sun: around 142 million miles (1.53 AU), on average.
Orbital Period: 687 days.
Rotational Period: once every 24.6 hours.
Notable Features and Facts: Mars is known as the “red planet,” but it really should be known as the “volcano planet.” Olympus Mons – the tallest, and widest volcano in the solar system – is also Mars’s widest and tallest mountain. Olympus Mons is 374 miles wide and 16 miles tall; for context, it is over two times taller than Mount Everest and as large as the state of Arizona.
Region Where Water is Located: the polar ice caps of Mars are visible through a telescope, actually. Water exists almost exclusively in the poles, but some scientists speculate that salty lakes could exist under the Martian polar surface.
Earth
Name Origination: Earth is the only planet in our solar system to have not been named after a Greek or Roman god; its name originates from the Germanic word for the ground.
Diameter: 7,918 miles.
Surface Gravity: 9.81 N/kg (1g).
Distance From the Sun: around 93 million miles (1 AU), on average.
Orbital Period: slightly over 365 days.
Rotational Period: slightly under 24 hours (23 hours, 56 minutes, 4 seconds).
Notable Features and Facts: Earth is the closest planet to the sun with a moon; it is also the only body in the solar system (besides comets when they are near the sun) with liquid water on its surface.
Region Where Water is Located: virtually everywhere.
Ceres
Name Origination: Ceres is named after the Roman goddess of corn and the harvests, Ceres.
Diameter: 587.82 miles.
Surface Gravity: .27 N/kg (.028g).
Distance From the Sun: around 257 million miles (2.76 AU), on average.
Orbital Period: 1,680 days (4.6 Earth years).
Rotational Period: 9 hours.
Notable Features and Facts: Ceres is the only dwarf planet known to exist in the asteroid belt. It was reclassified from an asteroid to a dwarf planet by the International Astronomical Union in 2006 (the same year Pluto was reclassified).
Region Where Water May be Located: the surface of Ceres is at most 30% water ice; Ceres also has liquid oceans under its surface.
Moons
Ganymede
Satellite of which Planet: largest moon in the Galilean group of moons – the group of the four largest satellites of Jupiter.
Name Origination: named after a boy who was made “cupbearer” for the Greek Gods.
Diameter: 3,273.5 miles.
Surface Gravity: 1.4 N/kg (.143g).
Rotational Period: 171 hours (a week and three hours).
Distance from the Sun: around 476 million miles from the sun, on average.🕇
Notable Features and Facts: Ganymede is slightly larger than the Saturnian moon Titan, and also slightly larger than Mercury, the smallest planet in the solar system. It is the only moon known to have a magnetic field.
Region Where Water May be Located: Ganymede has a massive saltwater ocean with more water than all of the water present on Earth; it is present deep under its surface, extending for sixty miles (ten times the depth of Earth’s deepest oceans and trenches).
Enceladus
Satellite of which Planet: Saturn.
Name Origination: named after a giant in Greek mythology, even though it is only as wide as Arizona.
Diameter: 313.3 miles.
Surface Gravity: .113 N/kg (.012g)
Rotational Period: 1.37 days.
Distance from the Sun: around 927 million miles, on average.
Notable Features and Facts: with an albedo of around .81 (+/- .04), Enceladus has the most reflective surface in the entire solar system.
Region Where Water May be Located: like Ganymede’s massive ocean under its surface, Enceladus, too, has a massive ocean under its surface. There are fractures in the crust in which water and other materials escape Enceladus, forming plumes and jets that have been observed by scientists at NASA.
Titan
Satellite of which Planet: Saturn.
Name Origination: Named after the Titans of Greek Mythology.
Diameter: 3,200 miles.
Surface Gravity: 1.354 N/kg (.14g).
Rotational Period: 15 days.
Distance from the Sun: 927 million miles, on average.
Notable Features and Facts: supposing that you have an air mask and something to keep you warm, you could theoretically walk around the surface without a spacesuit; Titan’s atmospheric pressure is actually comparable to that of Earth’s (around 1.5x Earth’s atmospheric pressure).
Region Where Water May be Located: I did somewhat bend the rules for Titan; the moon is known to have subsurface lakes of methane and ethane, which could theoretically support life – that life, however, would be much different than life on earth.
Callisto
Satellite of which Planet: Jupiter.
Name Origination: Callisto is named after a woman whom Zeus turned to a bear.
Diameter: 2,995 miles.
Surface Gravity: 1.236 N/kg (.13g).
Rotational Period: 16.7 days.
Distance from the Sun: 476 million miles, on average.
Notable Features and Facts: Callisto is among the incredibly colorful and craterous of all the moons in the solar system.
Region Where Water May be Located: Callisto is, too, believed to have a subsurface ocean.
Europa
Satellite of which Planet: Jupiter.
Name Origination: In Greek Mythology, Europa was the daughter of the Phoenician king Agenor.
Diameter: 1,940 miles.
Surface Gravity: 1.315 N/kg (.13g).
Rotational Period: 3.5 days.
Distance from the Sun: 476 million miles, on average.
Notable Features and Facts: Europa is regarded among conspiracy theorists and scientists alike as one of the prime candidates for extraterrestrial life in the solar system.
Region Where Water May be Located: strong evidence supports the existence of oceans below the surface of Europa, and massive plumes continue to be observed there.
Dione
Satellite of which Planet: Saturn.
Name Origination: from the Greek Goddess Dione, daughter of Tethys and Oceanus.
Diameter: 698 miles.
Surface Gravity: .223 N/kg (.023g).
Rotational Period: 2.74 days.
Distance from the Sun: 927 million miles, on average.
Notable Features and Facts: Dione orbits Saturn at a distance comparable to that of the moon to earth – Dione orbits around 234,500 miles from Saturn, whereas the moon orbits around 238,900 miles from Earth. Dione, however, orbits about Saturn every 2.74 days, much faster than the moon’s 27.3; because Saturn’s mass – and, therefore, its gravitational pull – is much stronger than earth’s, Dione must have a greater velocity to maintain a stable orbit.
Region Where Water May be Located: the Cassini Spacecraft discovered that Dione, too, likely has a subsurface saltwater ocean.
Mimas
Satellite of which Planet: Saturn.
Name Origination: from the giant Mimas, who was killed by Mars in the war between the Titans and Mount Olympus.
Diameter: 246 miles.
Surface Gravity: .064 N/kg (.0065g).
Rotational Period: like most of the Saturnian moons – including all those looked at today – Mimas is tidally-locked with Saturn; it completes a full rotation and revolution every .942 days.
Distance from the Sun: 927 million miles, on average.
Notable Features and Facts: A giant crater nicknamed Herschel – named after the discoverer of Mimas, William Herschel – is the most distinguishable feature of Mimas; the massive crater makes the moon look remarkably similar to the Death Star in Star Wars, although the crater was first discovered three years after the original Star Wars was released.
Region Where Water May be Located: Mimas’s low density suggests that it is composed almost entirely of ice water, but water may exist near the moon’s core.
Triton
Satellite of which Planet: Neptune.
Name Origination: after the son of Poseidon, Triton.
Diameter: 1,682 miles.
Surface Gravity: .779 N/kg (.08g).
Rotational Period: as with all other moons on this list, Triton is tidally locked with Neptune, orbiting Neptune and rotating every 5.9 days.
Distance from the Sun: 2.78 billion miles (30.1 AU)
Notable Features and Facts: Triton is the only large moon in the entire solar system to have a retrograde orbit; a retrograde orbit is essentially a celestial body – in this case, a moon – orbiting around a parent body – in this case, a planet – in the opposite direction relative to the planet’s rotation.
Region Where Water May be Located: Triton, too, may have a subsurface saltwater ocean, but because of its extremely long distance from the sun and its high density, it is unlikely that the ocean is anywhere near as large as those of the other satellites on this list.
Wrapping it up
Realizing that so many celestial bodies in our solar system could potentially harbor water and even possibly extraterrestrial life, we find remarkable cause for humility, understanding of our insignificance. It demonstrates to us that instead we may be statistically unimportant as only one planet of life existing in a much broader universe. As always, take care and stay curious, everyone.
* These are only the moons and planets theorized to have liquid water either on their surface or underground. Earth, although not mentioned, is included in the list. The list does not, however, include asteroids or comets that may have liquid water (although only some comets and asteroids that get very close to the sun have any liquid water).
☨ N/kg, or Newtons per kilogram, is a unit representing the strength of the gravitational force of an astronomical body. N/kg is dimensionally parallel to m/s/s, which is the unit for acceleration; an object on earth, for example, would be pulled with a force of 9.81 N/kg, and would accelerate towards the center of earth at a rate of 9.81 m/s/s.\
🕇 The average distance from the sun for all of the moons will be equivalent to their home planet’s distance; therefore, some information regarding distance may appear redundant.
References
Callisto In Depth. (2021, July 19). Retrieved from https://solarsystem.nasa.gov/moons/jupiter-moons/callisto/in-depth/
Ceres. (2021, August 05). Retrieved from https://solarsystem.nasa.gov/planets/dwarf-planets/ceres/overview/
Dione In Depth. (2019, December 19). Retrieved from https://solarsystem.nasa.gov/moons/saturn-moons/dione/in-depth/
Earth. (2022, March 29). Retrieved from https://solarsystem.nasa.gov/planets/earth/overview/
Enceladus. (2020, October 08). Retrieved from https://solarsystem.nasa.gov/moons/saturn-moons/enceladus/in-depth/
Europa. (2021, November 04). Retrieved from https://solarsystem.nasa.gov/moons/jupiter-moons/europa/in-depth/
Ganymede In Depth. (2021, November 10). Retrieved from https://solarsystem.nasa.gov/moons/jupiter-moons/ganymede/in-depth/
Greshko, M. (2021, May 03). Mars, the red planet: Facts and information. Retrieved from https://www.nationalgeographic.com/science/space/solar-system/mars/
John Wenz Writer John Wenz is a Popular Mechanics writer and space obsessive based in Philadelphia. (2022, March 11). 23 Places We've Found Water in Our Solar System. Retrieved from https://www.popularmechanics.com/space/a14555/water-worlds-in-our-solar-system/
Kramer, M. (2015, March 12). Jupiter's Moon Ganymede Has a Salty Ocean with More Water than Earth. Retrieved from https://www.space.com/28807-jupiter-moon-ganymede-salty-ocean.html
Mimas In Depth. (2019, December 19). Retrieved from https://solarsystem.nasa.gov/moons/saturn-moons/mimas/in-depth/
Titan - Overview. (2020, November 10). Retrieved from https://solarsystem.nasa.gov/moons/saturn-moons/titan/overview/
Triton In Depth. (2021, February 04). Retrieved from https://solarsystem.nasa.gov/moons/neptune-moons/triton/in-depth/
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