Europa's deep ocean may hold the conditions needed to support alien life

NASA explores Earth's deepest oceans to prepare for space

By studying extreme environments in Earth's hadal zone—the deepest part of the ocean —NASA tests technologies, probes life under crushing pressure, and gathers clues about potential oceans and possible life on worlds like Europa and Enceladus.

ESA’s Juice and NASA’s Europa Clipper will search for habitability near Jupiter

Three of Jupiter’s moons—Ganymede, Europa, and Callisto—possess subsurface oceans that may support life. While Clipper will perform flybys of Europa, Juice will be the first spacecraft to orbit a moon in the outer Solar System.

Why the existence of extremophiles greatly improves the odds of life beyond Earth

The conditions for life have long been thought to include liquid water, an energy source, and the essential elements for organic molecules within environments on or near Earth's surface. However, because extremophiles thrive in far more inhospitable environments, astronomers now analyze exoplanets whose characteristics indicate environments that fall within a broader range of possibilities when searching for signs of extraterrestrial life.

JWST might spot life faster on ocean worlds than Earth-like ones

Unlike Earth-like planets, hycean worlds with thick hydrogen atmospheres and deep oceans could allow biosignature gases like methyl halides to accumulate in detectable levels. These gases, linked to microbial life on Earth, are easier for the James Webb Space Telescope to identify than traditional markers like oxygen or methane.

Where should we look for extraterrestrial life?

Not all planets are created equal. Those capable of sustaining life as we known it must meet strict criteria, the most important of which is being at the right distance from their host star to have liquid water on the surface.

Exoplanet atmospheric gas patterns may indirectly provide evidence for life

When searching for life beyond the solar system, scientists first determine the range of distances from a star that liquid water—believed to be essential for life—can be found. Within this habitable zone, the presence of specific molecules in an exoplanet's atmosphere—detectable through spectral analysis—can indicate the presence of living things known to produce those compounds.

The warmest waters in the ocean are found at hydrothermal vents—hot springs on the seafloor that discharge plumes of mineral-rich water.

Earth's first oceans may have been as much as 230 degrees Celsius (446 degrees Fahrenheit), with atmospheric pressure preventing them from boiling.

A look at hydrothermal vents, where barophiles and hyperthermophiles survive boiling water

Discovered in 1977 during an exploration of the Galapagos Rift, these seafloor openings spew hot magma and chemicals that heat seawater to hundreds of degrees. Without the sunlight found at depths of less than 1,000 meters (3,281 feet), extremophiles in these environments convert released chemicals into energy to survive, alongside surviving extreme pressures.

Extremophiles were likely to have been Earth's first, and are expected to be its last, organisms

Their ability to survive in an enormous range of environmental conditions, including some resembling what has been modeled to have existed relatively shortly after Earth's formation, makes them the leading candidates for enduring the increasing solar intensity and the subsequent effects (e.g., zero-oxygen atmosphere, evaporated oceans) expected in the coming billions of years.

Aliens may be closer to Earth than scientists have previously assumed

The hunt for extraterrestrial life is often associated with traveling far into the depths of space for clues. But answers could be closer than we think. Modern space missions have demonstrated our capability of sending probes beyond the solar system, making it plausible that other civilizations could do the same.

Hypotheses on the origins of Earth's water, from comets and asteroids to magma oceans

Before Earth's atmosphere formed, any liquid water would have boiled off, preventing the accumulation of water early on to create today's oceans. Planetary scientists continue to debate whether this water was delivered later from comet or asteroid collisions or via reactions between iron oxide in Earth's molten surface and hydrogen gas from the planetary nebula.

The fortunate factors that make life on Earth possible

The Earth is teeming with life while all the other exoplanets and planets aren't. A very specific set of aligned factors forms the habitability of our planet, and without just one of these fortunate factors, we might not be here. This piece lists...

Abiogenesis explains how Earth's natural processes could have formed organic matter

The theory details how chemical interactions in hydrothermal vents and shallow ponds billions of years ago could have created lipids, proteins, and RNA. As these interactions involve water, life is thought to have started in oceans.

Visualize water's abundance across the solar system, and its relative rarity on Earth

Despite covering almost three-quarters of its surface, water only makes up about 0.12% of Earth's volume. Water in some of Jupiter's and Saturn's moons comprises a larger share of those celestial bodies and of the total water in the solar system. For example, Jupiter's moon Ganymede is believed to harbor almost nine times Earth's oceans beneath its icy shell.

Mars once had oceans and a thick atmosphere

It formed over millions of years as small clumps of matter orbiting the sun smashed together, solidified, and cooled. Geological features indicate the presence of past surface water, which evaporated away due to the planet's weak gravitational field.

The key ingredients to life on Earth—and elsewhere

Life can only arise in incredibly specific conditions, an abundance of certain substances like water and phosphorus, lots of time, and the right proximity to a heat-and-light-providing star. These two experts on evolution of life say above all, life requires luck. Here's a list of eight ingredients to life.

Earth's oceans, which have an average depth of 3.7 kilometers (2.3 miles), may be divided into zones based on depth or the abundance of light.

Why extremophiles may play an important role in terraforming Mars

Possessing unique biochemicals that can detoxify extreme environments and resilience against the Martian surface that is lethal to humans, scientists are exploring whether colonies of these organisms can transform small areas of the Red Planet into future habitats for humans. Extremophiles may also be best equipped to serve as microscopic factories for the fabrication of essential polymers.

Mold growth in space raises the hypothesis of life being brought to Earth

Panspermia suggests that life could be carried throughout the cosmos by asteroids, comets, and other objects, but it requires organisms that can withstand the extreme cold of space travel, stellar radiation, lack of water, and intense heat of planetary impacts. The discovery of mold on the International Space Station and experiments showing it can withstand radiation in outer space-like conditions increase the plausibility of the hypothesis.

Some marine life can survive the extreme pressure of the deep ocean because of specialized molecules that strengthen proteins, enzymes, and cellular membranes.

As of 2025, humans have only dug 0.2% the way to Earth's center

The Kola Superdeep Borehole revealed two billion-year-old fossils and underground water, but the immense temperature and pressure prevented further tunneling. Beyond those depths, scientists know of Earth's interior by analyzing how seismic waves move.

Metallic hydrogen exists in Jupiter and Saturn due to high pressure and temperature

This state of hydrogen has metallic properties, including conductivity, which powers these planets' magnetic fields. First theorized in the 1930s, its existence was confirmed through indirect evidence before being created in a Harvard lab in 2017.

Just as the moon deforms the Earth to create tides, Jupiter deforms its moon, Io, generating the thermal energy in Io's interior that powers the more than 400 volcanoes on its surface.

Explore the deepest parts of the ocean

The deeps of the Earth's oceans are some of the most extreme environments on the planet. Take a trip 36,000 feet to the deepest parts of the sea in this informative, 10-minute animated video.

Io, Jupiter’s moon, is the most volcanically active body in the solar system

The innermost and third-largest of Jupiter’s four Galilean moons, Io’s volcanic activity is driven by tidal heating from Jupiter’s gravitational pull. Its atmosphere is very thin and primarily composed of sulfur dioxide, and its volcanic eruptions can exceed 1,000°C.

Juno has revealed Jupiter’s polar cyclones, complex atmosphere, and diffuse core

The continent-sized cyclones at Jupiter’s poles generate strong winds and ammonia-laden storms. The spacecraft has also collected data on Jupiter’s unique magnetic field, which resembles a blend of Earth’s and Uranus/Neptune's.

Ceres—the largest object in the asteroid belt—may have once harbored a muddy ocean

NASA's Dawn mission revealed Ceres' surface composition, which contains salts, water ice, and organic material. Ceres' ocean likely froze over entirely in the past, when the presence of water may have allowed life to exist.

View a gallery of animals found on abyssal plains, hydrothermal vents, seamounts, and other deep-sea habitats.

The thousands of objects orbiting Jupiter include 95 officially recognized moons

Jupiter's moons were first discovered on Jan. 7, 1610. They include Ganymede, the largest moon in the solar system and larger than Mercury, Io, the most volcanically active moon, and Europa, which has a saltwater ocean.

Remnants of another planet that helped form the moon may be beneath Earth's surface

Large mantle structures beneath Africa and the Pacific Ocean may be the buried remains of Thea, a large Mars-sized planet that collided with Earth. The theory is supported by isotopic evidence from volcanic and lunar rocks.

How we know what's deep inside the Earth, despite never traveling there

We'll likely never see the Earth's core, but we can make educated guesses about what it's like down there. Nearly as hot as the sun's surface and under impossibly high pressure, the inner Earths extreme conditions make it impossible to explore. Yet, seismic waves during earthquakes, volcanic eruptions, and light waves from the sun provide fascinating insights about our planet's mantle, crust, and core.

Learn about endoliths, the polyextremophiles that thrive inside rocks

These organisms include species that live in Antarctica, where they perform photosynthesis using light and water that makes it through pores in sandstone. Others residing in Earth's crust can survive temperatures reaching 60 degrees Celsius (140 degrees Fahrenheit) while generating energy through chemical reactions involving nutrients and gases trapped in rocks.

One of the hottest known exoplanets seems to snow an active ingredient of sunscreen, titanium dioxide—but only on the dark side of the planet.

Can coral live in cold water?

Dive deep beyond the sunlit coral reefs, and you'll discover a world of deep-sea corals. This article from the National Oceanic and Atmospheric Administration (NOAA) explores the ecosystems of deep-sea corals found way below the water's surface....

Although an estimated 99.999% of the deep ocean has not been explored, techniques such as sonar have been used to identify the deepest known point in each of Earth's five oceans.

Lining up every microbe on Earth would stretch to about 105,000 light-years

There are about 10²⁷ such organisms on the planet, many of which are adapted to produce energy through uncommon reactions in unconventional environments, such as within rocks or near volcanoes on the ocean floor. Studies of these organisms have reframed astrobiologists' search for life beyond Earth by broadening the parameters under which life can exist.

Planetary exploration and the search for extraterrestrial life kicked off with Viking

NASA's Viking 1 and 2 missions revealed Mars' geological activity and potential for past life through their evidence of past surface water. Viking 1 held the record for the longest Mars surface operation until the Opportunity rover surpassed it in 2010.

Extraterrestrial volcanoes spew material present during their formation

Unlike Earth's volcanoes that release lava, cryovolcanoes on distant moons erupt cold jets of water, ammonia, and other light gases present during the formation of their host planet. The movement of internal heat produced during formation is thought to drive icy plume movement.

Early Earth lifeforms likely made energy via mineral reactions, not sunlight

Earth's initial atmosphere was filled with carbon dioxide, methane, and water, with most oxygen locked away in the rocky crust. Over time, bacteria evolved to slowly release that oxygen into the atmosphere by breaking down rock.

Scientists break down the plausibility of the alien world depicted in 'Avatar'

The film series created by James Cameron raises several interesting questions about whether certain technological advancements are feasible, and if extraterrestrial life could thrive on a moon orbiting a distant gas giant. While Pandora—the moon that the Na'vi people live on—could, in theory, exist, it's unlikely that its residents would be so humanlike.

If the sun disappeared, we would not know about it for 8 minutes and 20 seconds, at which point the Earth would suddenly move in a straight line on its way out of the solar system.

Although no such planet exists in our solar system, the most common subtype of exoplanet in the galaxy is the sub-Neptune world, which is larger than Earth but smaller than the ice giants.

The Hubble Space Telescope made discoveries within our solar system and across the universe

The observatory helped confirm the presence of water on Jupiter's moon Europa, and uncovered seasonal variations on planets like Uranus. It also observed exoplanets and gravitational lensing, proved the existence of supermassive black holes at the centers of galaxies, and detected the accelerated expansion of the universe.

Scientists investigate Earth's interior by studying seismic waves

Scientists investigate Earth's interior by studying seismic wavesBelow Earth's atmosphere lies the crust, which extends to the Mohorovičić discontinuity between five and 20 miles below Earth's surface. Below the crust lies the mantle, the liquid-metal outer core, and the solid inner core, which surpasses 5,200 degrees Celsius (9,392 degrees Fahrenheit).

Questioning the results of life on K2-18b

An analysis of the atmosphere of an exoplanet called K2-18b identified the presence of biosignatures—molecules that are created by living things on Earth. This discovery may indicate life exists beyond Earth, but the lack of environmental data complicates the interpretation of results.

Tidally locked exoplanets experience extreme atmospheric temperatures

On worlds like WASP 76b, which orbits its host star approximately 3% the Earth-sun distance, temperatures on its day side can vaporize iron. Winds more than 14 times the speed of sound blow this material to its night side, where it condenses and falls as liquid metal.

The 300-million-year period where Earth looked like a snowball

Life has existed on Earth for at least 3 billion years, but the planet has not always looked like it does today. Rather than the blues and greens of our modern globe, for a 300 million-year period, the Earth was covered in ice and snow, from the poles to the equator. Surprisingly, life was thriving at the time.

Jupiter’s formation included accretion and migrations across the solar system

One theory of Jupiter’s formation involves the planet spiraling inwards from the asteroid belt, gathering material and disrupting the initial formation of terrestrial planets. Saturn’s gravitational pull would then reverse its course.

Panspermia, the theory that cellular life came from a different planet

One of the most profound mysteries of human life on earth is the presence of living cells: organic, self-organizing, reproducing creatures with a drive to survive within given set conditions. Traditional theories posit life came from divine...