Scientists recently found
even more evidence that Jupiter's icy moon Europa is hiding an enormous ocean
of saltwater. To say Europa's ocean is vast would be an understatement. If all
of Earth's water — oceans, lakes, rivers, rain, clouds, and more — were
combined into one blob, it'd be just half as large as Europa's liquid
reservoir. (And Europa is about the size of Earth's moon.)
Scientists think Europa's
ocean might even be habitable to alien life.
"If there's life at
Europa, it'd almost certainly be an independently evolved form of life,"
Bob Pappalardo, a planetary scientist at NASA's Jet Propulsion Laboratory,
previously told Business Insider. "Would it use DNA or RNA? Would it use
the same chemistry to store and use energy? Discovering extraterrestrial life
would revolutionize our understanding of biology."
But Europa is just one of
many ocean worlds in the solar system, including Enceladus, Pluto, Titan, and
Ganymede. To figure out how much liquid water and ice these worlds have
compared to Earth, Business Insider contacted Steve Vance, a planetary
scientist at NASA's Jet Propulsion Laboratory. Vance closely monitors research
about ocean worlds to create estimates of ice thickness, ocean depth, and other
parameters.
The graphics shown below use
the Vance's data and other sources to show the probable volume of the liquid
water on eight known ocean worlds besides Earth.
Volumes are shown in
zettaliters (ZL), a unit that's equal to 1,000,000,000,000,000,000,000 liters
or 1 billion cubic kilometers. Earth harbors about 1.335 ZL of water, according
to the National Oceanic and Atmospheric Administration.
Enceladus is a relatively
small moon of Saturn, at just 314 miles in diameter — about as wide as the
state of Arizona. But its ocean sprays water into space. NASA's Cassini
spacecraft confirmed the ocean's existence after its arrival in 2004, later
detecting and flying through the water plumes to "taste" them..
Note: Because Earth has a
very small amount of ice relative to other ocean worlds, this graphic and the
following ones only depict our planet's liquid water.
Triton is a moon of Neptune that's some 2.8 billion miles
from Earth. Voyager 2 is the only spacecraft ever to fly by, measure, and
photograph Triton. Those sequential photos showed that Triton has
"cryovolcanoes" that spew out water and ammonia. It’s one of the most
fascinating world in our solar systems.
Dione is a small, icy moon
of Saturn. Scientists determined in 2016 that — like Enceladus — Dione likely
has a subsurface ocean.
Pluto is the famous planet of yesteryear that astronomers
agreed to demote to a dwarf planet. NASA's New Horizons spacecraft recently
helped determine that Pluto has a liquid ocean packed with ammonia— a substance
that's toxic to humans, but could feed alien microbes.
Europa is the smallest of
four Galilean moons of Jupiter (so named because they're the largest and were
first discovered by Galileo Galilei in 1610). Europa is about the size of
Earth's moon and likely has a huge, salty ocean. Volcanoes on Io, the
second-largest Galilean moon, likely burp out sulfur-rich nutrients that then
enter Europa's ocean.
Recent studies also suggest
that Europa is shooting out jets of this ocean water into space — where a
future spacecraft could sample them for signs of life.
Callisto, the second-largest
Galilean moon, is covered in ice,= and almost certainly has a vast ocean.
However, its crust is about 125 miles thick — which makes it very difficult for
scientists to discover what's going on down there.
Titan is the largest moon of
Saturn and the second-largest moon in the solar system. Scientists often refer
to it as a "proto-Earth" due to its composition and size. A similarly
colossal ocean of liquid water may exist below its roughly 60-mile-thick crust
of ice.
Ganymede is the largest of
Jupiter's Galilean moons, and the biggest moon in the solar system. Its stores
of water may outnumber Earth's by a ratio of 18 to one.
Earth is much bigger than
other ocean worlds in the solar system, but Europa, Pluto, and others have
bigger oceans of liquid water. Jenny Cheng/Business Insider
In order of how much water
each world has, from the least to the most, the wettest are: Enceladus, Dione,
Earth, Europa, Pluto, Triton, Callisto, Titan, and Ganymede. Mimas, a moon of
Saturn, and Ceres, the largest asteroid in the solar system, might also have
subsurface oceans. But scientists aren't yet sure how big each one might be, if
they exist at all. So what do you think? Could alien life exist on these
worlds?
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