Last week brought the news that Enceladus likely has a warm salty ocean , and that liquid water lurks beneath the surface of Ganymede. These findings are continuing to chip away at the once-held belief that the solar system was dry and barren, bereft of water. The hunt for extraterrestrial life has turned to our own cosmic backyard.
It seems there are few places in the solar systems without some amount of water, whether liquid or solid. There's even a small amount of water vapor on Venus, something like 20 parts-per-million. And every time a source of liquid water is found or suggested, it brings up the chances of life on that world because of the way water acts as a solvent — facilitating the metabolic processes at the most basic level of life.
That's why the hunt for extraterrestrial life quite doubtfully of an intelligent sort, though we've found some quite remarkable octopuses on Earth has turned from distant solar systems to our own cosmic backyard.
Here's the breakdown of all the water we know about in the solar system, and what form it comes in. Europa has been the biggest contender for life for years now, with a craggy icy crust hinting in almost every way at an ocean below. Thanks to the tidal effects from Jupiter friction inside the moon created by the pull of the planet's gravity , the water would be kept liquid and possibly even warm below the icy crust, helped by possible hydrothermal vents.
There's been some evidence of ice geysers shooting from the surface of Europa, as well as evidence that the ocean could have Hadley Cells —warm water radiating from the moon's equator. Europa could provide the possibility not just for life, but, if the conditions were just right, even complex life. We've known of tiny, sleepy Enceladus since The diameter is just miles, smaller even than Ceres and Vesta, the two largest objects in the asteroid belt.
Compare that to Europa, slightly smaller than our Moon at a 1, mile diameter. Never mind its small size: This is one of the most intriguing places in the solar system and best candidates for a warm, wet, salty ocean. It has as high a probability for life, if not higher, than Europa.
Enceladus orbits near the rings of Saturn. In fact, watery eruptions from Enceladus' ice geysers comprise the F-Ring of the gas giant—the moon spews 1, tons of water into space every hour, according to Phil Plait at Bad Astronomy , along with organic molecules, salt, and other materials. Recent research suggests the ocean is also very warm thanks to the tidal effects from Saturn.
The tug causes hydrothermal activity, which warms the oceans and causes the geysers, all in the kinds of hot beds that sprouted life on Earth. Ganymede is the largest moon in our solar system, bigger than even the planet Mercury.
Astronomers had long suspected that an ocean lies beneath the mile-thick ice crust at the surface, and in a new study , aurorae activity suggest that the ocean is somewhat warm and definitely salty. Unlike Europa, no ice geyser activity has yet been spotted.
This could be because of a reduced tidal effect on the moon, which is further from Jupiter than Europa. Unlike Europa, it doesn't have the cross-hatched icy surface showing consistent geologic surface activity.
Still, the signs are good that Ganymede is harboring an ocean. Callisto is similar in composition to Ganymede and, as the furthest out of the four Galilean moon of Jupiter, is bombarded with the least amount radiation.
It also has a magnetic field, adding some additional protection. We know there's water here—what we don't know is to what extent it's liquid. Callisto's relative lack of geologic activity suggests that the moon might not be able to sustain an ocean without the presence of some kind of anti-freeze compound within, meaning that there could be just a whole lot of ice in there. However, as the farthest out of the satellites, it could make an interesting destination for exploration, allowing you to avoid the harsher effects of Jupiter's radiation while remotely exploring the other moons for signs of oceans and life.
The Red Planet probably once had oceans, including one covering a good chunk of the northern hemisphere. There are traces of water left on the surface, including compounds from the evaporation of the ancient ocean, as well as seasonal water ices covering the surface of the planet. There is some evidence pointing to occasional melting on the surface as well.
That much is clear. But there's an intriguing possibility that Mars still has water underneath the surface, possibly in the forms of aquifers. Theoretically, these underground waterways could still host microbial life under the surface of Mars. Login or Register Customer Service. RISE —. PHASE —. Tonight's Sky — Change location. US state, Canadian province, or country. Tonight's Sky — Select location. Tonight's Sky — Enter coordinates.
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Astronomy Day. The Complete Star Atlas. A crescent Neptune hangs in the background, while the Sun appears as only a bright star in the upper left. Both appear as crescents in this image taken by Voyager 2 just over three days after its closest approach to the system.
Ocean worlds abound in the solar system. Europa and Enceladus may be the best known after Earth, but dwarf planets Pluto and Ceres are also candidates for hosting liquid water beneath their surface. Even some of the largest chunks of ice at the edge of the solar system could have water under the surface. Several years ago, at a meeting of planetary scientists, she recalls that many of the Earth-focused oceanographers present were confident that an extraterrestrial ocean would lead to the discovery of life.
These features were formed by blobs of salt, rather than ice, rising to the surface. A hidden ocean Voyager glimpsed Triton only briefly, but that glimpse was tantalizing enough. Heating an ocean Triton was born in the Kuiper Belt, the ring of icy rocks orbiting the Sun beyond the planets. Researchers believe these streaks are deposits of material from geysers past and present.
Voyager snapped this color image of Triton, constructed from three separate images through different filters, on August 23, The bigger picture Understanding whether Triton has an ocean is key to understanding not only the potential habitability of the small moon, but also establishing the way life may evolve elsewhere in the solar system. The new research calculates how the thickness of the ice shell can influence the tidal dissipation and thus the crystallization of the subsurface ocean.
If Triton's ice shell is thin, then the tidal forces will have a more pronounced effect and increase the heating. If the shell is thick, then the moon becomes more rigid and less tidal heating will occur. If the core turns out to be larger than the value used in the calculations, then there will be more radiogenic heating, with extra heating increasing the size of any existing ocean. The depth of the ocean also may not be constant across the moon, as tidal dissipation concentrates energy near the poles, meaning that an ocean would likely be deeper there.
In addition, recent calculations estimate that icy bodies in the outer solar system could be comprised of up to 15 percent ammonia. Ammonia-rich volatile material works to lower the temperature at which a solid turns to a liquid, and the presence of such volatiles may also help a liquid layer persist beneath the ice. Subsurface oceans on icy solar system bodies could provide potential habitats for primitive extraterrestrial life.
Jupiter's moon Europa is currently the leading candidate for such a habitat, although there is still much debate about this. The probability of life existing within the depths of Triton's ocean is much smaller than for Europa, but it still can't be completely ruled out, researchers say.
The ammonia that is likely present in Triton's subsurface ocean might act to lower the freezing point of water, thus making it more suitable for life. The temperature of the ocean is still probably around minus degrees Fahrenheit minus 97 degrees Celsius , which would slow down biochemical reactions significantly, and impede evolution.
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