object

europa

A moon of Jupiter with a subsurface ocean, used as a benchmark for habitable conditions in this study.
66 related articles

Description

Europa is the fourth-largest moon of Jupiter and one of the most promising candidates for hosting habitable environments beyond Earth. Its icy surface hides a global subsurface ocean of liquid water, kept warm by tidal heating from Jupiter's gravity. This makes Europa a benchmark for studying the conditions necessary for life and a target for future space missions.

History

The idea of a subsurface ocean on Europa was proposed in the 1970s based on Voyager images showing a young, cracked surface, and strongly supported by Galileo spacecraft measurements of its magnetic field in the 1990s.

How it works

Europa's interior is heated by tidal flexing: as it orbits Jupiter, the planet's gravity stretches and relaxes the moon, generating friction that melts the ice below the crust. This heat maintains a liquid water ocean beneath a shell of ice, and the ocean is in contact with a rocky seafloor, providing chemical energy sources that could support microbial life.

In practice

Europa is the target of NASA's Europa Clipper mission, which will study its ice shell and ocean to assess its habitability and prepare for future landers.

Fun fact

Europa's ocean may contain more than twice the volume of all Earth's oceans combined, despite the moon being only a quarter of Earth's size.

Concept graph →

Related articles · 67

Mars's Salt Thermos
Every Martian night, salt crystals on the planet's surface soak up moisture from the thin air, much like a sponge draws water from a damp cloth. By morning, a microscopic brine accumulates inside them, and during the day, as temperatures rise, that brine finds itself trapped in tiny cavities.
The Neighbor Who Wasn't Kicked Out
On a sunny street, there's a house with a big family: a giant father who always sits by the window and a small child running around the yard. That's the TOI-4468 system: a gas giant hot Jupiter hugs the star, while a bit farther out circles a sub-Neptune — a planet smaller than Neptune but larger than Earth.
Exoplanets2026-08-181 minarXiv:2608.17689express
Icy Moon in Radio Waves
From 1987 to 1991, astronomers last measured how Jupiter's icy moons reflect radio waves. Then came a long pause. In 2011–2024, researchers aimed a radar beam at Europa again: this time using the 70-meter antenna at Goldstone and the Green Bank Telescope. Ice is nearly transparent to radio waves, like clear window glass is to light.
Exoplanets2026-08-181 minarXiv:2608.17689express
Icy Moon in Radio Waves
From 1987 to 1991, astronomers last measured how Jupiter's icy moons reflect radio waves. Then came a long pause. In 2011–2024, researchers aimed a radar beam at Europa again: this time using the 70-meter antenna at Goldstone and the Green Bank Telescope. Ice is nearly transparent to radio waves, like clear window glass is to light.
Exoplanets2026-07-282 minarXiv:2607.25542express
Three Cloud Layers of Jupiter
Jupiter's atmosphere resembles a layered cake, where each layer plays its role. Scientists took data from four instruments at once (VLT/MUSE, Cassini/VIMS, IRTF/SpeX, and Juno/JIRAM) and built a model of clouds and ammonia in the planet's equatorial zone, from 0.1 to 10 bar (pressure equivalent to hundreds of kilometers below Earth's…
Exoplanets2026-07-212 minarXiv:2607.19579express
Heavy Water on a Hot Jupiter: WASP-39 b Surprises Astronomers
Water comes in different varieties. Not just fresh or salty, but also "heavy"—when one of its hydrogen atoms is replaced by deuterium, its heavier cousin. Such water is called HDO, and it's a true cosmic passport: the amount of deuterium in water reveals where and when that water was born.
Tidal Swings of an Eccentric Jupiter
Every 165 days, the giant planet dives toward its star, nearly grazing its fiery corona, then flies off into the icy void. This is TIC 241249530 b — an exoplanet with a record eccentricity of 0,94.
Icy Origins: Most Hot Jupiters Come from the Cold
Among the scorching exoplanets that circle perilously close to their stars lies the secret of their birth. Nearly three decades ago, Michel Mayor and Didier Queloz discovered the first such world, and since then astronomers have been tormented by the question: how does a gas giant end up pressed against…
Exoplanets2026-07-112 minarXiv:2607.10403express
Lunar muons could illuminate subsurface voids
The Moon is an airless sphere of dense rocky grit called regolith. When fast particles from space slam into it, muons are born in the soil — unstable relatives of electrons, but two hundred times heavier. Most fly downward and fade away in the depths. But those that pop upward into the vacuum can travel tens of kilometers before decaying.
Cosmic Debt: How a Planet's Mass Locks Civilizations Forever
Every civilization is born with a gravitational debt. The home planet's mass determines the loan amount, and the Tsiolkovsky equation is the interest rate applied to each kilogram of payload. To send a probe to the stars, you have to pay with fuel, and the debt grows exponentially.
Exoplanets2026-06-292 minarXiv:2606.30644express
How Giant Planets Hide Hydrogen Inside
A sub-Neptune is a planet that falls between Earth and Neptune in size. These worlds are abundant in our galaxy, but their internal structure has been hotly debated. New research shows that in their youth, these planets behave like a sponge soaked with water.
Exoplanets2026-06-222 minarXiv:2606.23483express
Mars's Subsurface Life: Radiation as Fuel
The Martian surface is a place where anything alive quickly dies. Cosmic rays and ubiquitous oxidizers sterilize the top layer of soil. But dig a little deeper, and the picture changes. There, beyond the reach of ultraviolet light, a zone suitable for life may lurk. This zone runs on a strange fuel — radiation.
Exoplanets2026-06-221 minarXiv:2606.23789express
James Webb Fishes Out an Invisible Planet from a Dusty Disk
Using James Webb, astronomers 'fished out' a third giant planet from the murky dust disk of the star β Pictoris. Two others were already known, but this one was hiding in the bright light, like a fish in muddy water.
Exoplanets2026-06-182 minarXiv:2606.20789express
How Tidal Waves Sort Planets
A pot of boiling soup is shaken hard — the liquid sloshes, waves crash against the walls. Something similar happens inside a gas planet when it swings past its star on an elongated orbit. The star's gravity excites powerful internal waves in the planet, known as tidal fundamental modes. These waves can completely change the planet's fate.
Exoplanets2026-06-161 minarXiv:2606.18219express
Inside Uranus and Neptune Lie Oceans of Magma
Previously, Uranus and Neptune were considered ice giants because of assumed thick layers of frozen water, methane, and ammonia. New calculations paint a different picture: deep inside them hides an ocean of hot magma, which under immense pressure has absorbed a colossal amount of hydrogen.
Exoplanets2026-06-161 minarXiv:2606.18355express
The Iron Planet Isn't So Iron After All
A cosmic sprinter on a short track: that's how you might describe planet GJ 367 b. It whips around its star in just 7.7 hours. This world is slightly smaller than Earth but has a personality: it was once thought to be nearly a solid ball of iron.
Exoplanets2026-06-111 minarXiv:2606.13350express
Mysterious Trace on Titan's Surface
The atmosphere of Titan, discovered by Christiaan Huygens, is opaque to ordinary telescopes. But spectral analysis finds 'windows' of transparency — narrow regions where the haze parts.
Cosmic Tan: How Stellar Flares Repaint Water Worlds
When astronomers peer at distant worlds, they often don't see crisp lines of water vapor or methane, but a blurry silhouette, as if the planet has thrown on a thick veil. This veil, a haze of organic particles, behaves like a temperamental photographic plate: it darkens under harsh ultraviolet light, revealing hidden chemical patterns.
Neptune's False Note: Nereid — Not an Interloper, but a Last Survivor
Among the hundreds of moons in the Solar System, Nereid dances the most desperate dance: diving toward Neptune as close as 1.4 million kilometers, then soaring away to 9.7 million — all within less than an Earth year. An eccentricity of 0.75 — the brand of a captured wanderer.
Exoplanets2026-05-212 minarXiv:2605.22931express
Catching a Sunset on a Distant Planet
When a planet slips behind the edge of its star, the star backlights the planet's atmosphere, just as a setting sun illuminates clouds on the horizon. This brief moment, lasting only minutes, carries the imprint of the gases through which the starlight has passed.
Exoplanets2026-05-151 minarXiv:2605.15595express
Martian Spores: How Life Could Have Flown to Earth
The idea of extraterrestrial origin of life has long excited minds. Fred Hoyle believed bacteria travel between stars. A new study tested a similar but closer route: from Mars to Earth. In ancient times, Mars had water, and asteroid impacts knocked rocks with microbes into space.
Exoplanets2026-05-061 minarXiv:2605.04840express
Mars's dense layer reveals the fate of rocky planets
If you don’t stir a layered cocktail, the heavy syrup sinks to the bottom. A young planet is much the same — a seething ocean of molten rock. As it cools, minerals crystallize: some, like iron, get heavy and sink, while others float. You’d think a dense layer would pile up at the core.
Exoplanets2026-05-032 minarXiv:2605.02036express
Exoplanets2026-05-022 minarXiv:2605.01589express
A Planet Where Day Melts Hydrogen and Night Hides Clouds
Planet WASP-121 b always shows the same face to its star, like a rock in a campfire. The dayside is so hot that ordinary hydrogen, the very stuff most of the universe is made of, can't take it: its molecules tear apart into individual atoms, and the temperature flips upside down: the higher you go, the hotter it gets.
Exoplanets2026-04-281 minarXiv:2604.25253express
Jupiter's Tail Is Wired Differently
A planet's magnetic field is like an invisible shield: it catches charged particles from the solar wind and stretches out behind the planet into a long tail, like a fluttering scarf.
General Relativity2026-04-141 minarXiv:2604.12787express
Planet Nine Heats Up with Dark Matter
At the edge of the solar system, far beyond Neptune's orbit, something is knocking icy chunks off their paths. Their orbits are stretched and tilted in the same way, as if an invisible hand arranged them in a pattern.
Exoplanets2026-04-132 minarXiv:2604.11911express
A Lava World with a Cool Face
A hot skillet on the stove glows in the dark, but if you cover it with a lid, the heat escapes more slowly and the surface doesn't look as bright. That's roughly the situation on planet HD 3167 b: it always shows the same face to its star, and the dayside is heated to temperatures that melt rock.
Exoplanets2026-04-062 minarXiv:2604.05235express
Moons of Distant Planets: What's Keeping Us from Seeing Them
The light from a distant star is never steady. It shimmers like heat over hot asphalt. When astronomers pointed JWST at the star TOI 700, they saw this shimmer especially clearly: every 16 minutes, the brightness changed by a tiny fraction, just 46 parts per million.For comparison: if you placed a light bulb a kilometer away, this change would be…
Instrumentation2026-04-021 minarXiv:2604.01927express
Europa's Ice Under Electron Fire
Europa's surface is an icy armor continuously bombarded by charged particles from Jupiter's magnetosphere. Electrons slam into the ice's crystal lattice, lose energy, and kick off chemical reactions. Until now, there was no tool to show how deep such bombardment pierces the ice.
Instrumentation2026-04-021 minarXiv:2604.02242express
Mars Without Biology: Three Paths to Warmth
Mars is an icy desert with an average temperature of minus 60. To warm it without biology, scientists propose three approaches with a single idea: create a thick heat-trapping blanket. First, deploy transparent film-blankets over bases. They let sunlight in but keep heat from escaping, allowing us to harvest water from the soil and grow plants.
Exoplanets2026-03-262 minarXiv:2603.24944express
Stellar Flares as a Source of Life
Water isn't the only thing life needs. To assemble the first RNA-like chains from simple molecules, you need ultraviolet light, like the sunlight that helps plants, but harsher and with shorter wavelengths. Big stars like the Sun emit plenty of this light. Small, dim stars, however, have almost none: they shine mostly in red and infrared, like a glowing ember.
Exoplanets2026-03-231 minarXiv:2603.22491express
How Bacteria Battle on Water Planets
Simple equations that describe fox and rabbit cycles have been turned to bacteria on distant exoplanets, like K2-18 b. These worlds hold deep oceans under thick hydrogen skies. Like duckweed on a pond, light-eating microbes cover the sunlit water surface, stealing light from those below.
Exoplanets2026-03-231 minarXiv:2603.22602express
Enceladus's Ocean — A Perfect Heat Pump
Beneath Enceladus's icy crust churns an ocean, acting like a perfect heat pump. It pushes heat from the equator to the poles, spending a thousand times less energy than it transports — like a perpetual motion machine built into the moon. The secret lies in salt.
Space Physics2026-03-111 minarXiv:2603.10760express
Beams from Jupiter's Poles
Above Jupiter's poles, auroras blaze as electrons are accelerated by electric fields and slam into the upper atmosphere, making the gas glow. But not all electrons head downward. Some, it turns out, get a kick in the opposite direction — away from the planet, into deep space.
Exoplanets2026-03-091 minarXiv:2603.08780express
A Cold Giant Wrapped in Icy Clouds
Around the star Epsilon Indi, visible to the naked eye from the Southern Hemisphere, orbits a planet the size of Jupiter. The temperature there is like a good freezer: minus 200 degrees Celsius. The James Webb Space Telescope has for the first time directly imaged it and measured the light the planet emits in the thermal range.
Exoplanets2026-02-281 minarXiv:2603.00385express
A Warm World Around a Quiet Star
Every 3.97 days, the disk of the star TOI-1080 dims slightly. The shadow lasts a few hours — a planet passing in front of its star, like a fly in front of a lamp. Such 'eclipses' are caught by the TESS space telescope, which watches thousands of stars at once.
Exoplanets2026-02-281 minarXiv:2603.00402express
Why a Tent on Mars Beats a Full-Blown Planetary Makeover
Today's Martian surface is a cold, nearly airless home. Many dream of a full renovation: warming the planet, filling it with air from carbon dioxide and nitrogen.
Stellar2026-02-261 minarXiv:2602.22979express
How a Swallowed Planet Spun Up a Star: The Case of GJ 504
GJ 504, a star almost the same age as our Sun, is spinning with remarkable vigor: it completes a full rotation in just 3.4 Earth days, while actively emitting X-rays. For comparison, typical stars of the Sun's age rotate much more slowly, as if they've lost their youthful energy. GJ 504, however, behaves like a figure skater who has received a powerful push and launched into a rapid spin.
Exoplanets2026-02-241 minarXiv:2602.20789express
Why Red Dwarfs Have Fewer Chances for Photosynthesis
Oxygenic photosynthesis requires splitting water. It's kind of like a water wheel: to make it spin, you need a strong current. Light acts as the current, and light particles are the streams. For red dwarfs, the most common stars, the light is "cool" and weak — the streams barely move the wheel.
Exoplanets2026-02-232 minarXiv:2602.19986express
Sodium in the Sky of a Distant Planet
When a planet passes in front of its star, some starlight filters through its atmosphere. Gases in the atmosphere block certain colors and let others through, like the colored glass of a stained-glass window. By seeing which colors are dimmed, you can figure out what the air of a distant world is made of.