What Can We Learn Flying Through the Plumes at Enceladus?

The Cassini spacecraft captured this image of cryovolcanic plumes erupting from Enceladus' ice-capped ocean. Image Credit: NASA/JPL/CalTech

In the next decade, space agencies will expand the search for extraterrestrial life beyond Mars, where all of our astrobiology efforts are currently focused. This includes the ESA’s JUpiter ICy moon’s Explorer (JUICE) and NASA’s Europa Clipper, which will fly past Europa and Ganymede repeatedly to study their surfaces and interiors. There’s also NASA’s proposed Dragonfly mission that will fly to Titan and study its atmosphere, methane lakes, and the rich organic chemistry happening on its surface. But perhaps the most compelling destination is Enceladus and the lovely plumes emanating from its southern polar region.

Since the Cassini mission got a close-up look at these plumes, scientists have been aching to send a robotic mission there to sample them – which appear to have all the ingredients for life in them. This is not as easy as it sounds, and there’s no indication flying through plumes will yield intact samples. In a recent paper, researchers from the University of Kent examined how the velocity of a passing spacecraft (and the resulting shock of impact) could significantly affect its ability to sample water and ice within the plumes.

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Saturn’s “Death Star Moon” Mimas Probably has an Ocean Too

Saturn's moon, Mimas, captured by NASA's Cassini spacecraft in 2010. (Credit: NASA/JPL-Caltech/Space Science Institute)

A recent study published in Nature presents a groundbreaking discovery that Saturn’s moon, Mimas, commonly known as the “Death Star” moon due to its similarities with the iconic Star Wars space station, possesses an internal ocean underneath its rocky crust. This study was conducted by an international team of researchers and holds the potential to help planetary geologists better understand the conditions for a planetary body to possess an internal ocean, which could also possess the conditions for life as we know it. While Mimas was photographed on several occasions by NASA’s Cassini spacecraft, including a close flyby in February 2010, what was the motivation behind this recent study regarding finding an internal ocean on Mimas?

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17 Known Exoplanets Could Have Oceans of Liquid Water

Astrobiologists believe that the Solar System's ice worlds are some of the most interesting places to search for life. These are moons or dwarf planets with thick ice shells surrounding oceans of liquid water - the perfect habitats for life. A new NASA study has found 17 exoplanets that have the right size, density and distance from their stars, and are probably similar to Europa or Enceladus and might even have geysers blasting water into space. Image Credit: NASA

The search for life is tied to the search for liquid water. That’s why astronomers are so keen on detecting rocky, Earth-like exoplanets in their stars’ habitable zones. In a habitable zone, a planet receives enough energy from its star to maintain liquid water on its surface, given the right atmospheric conditions.

But in our Solar System, we’ve found worlds with liquid water that are way beyond the habitable zone. Can we do the same in other solar systems?

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Europa Clipper Could Help Discover if Jupiter's Moon is Habitable

Artist's concept of a Europa Clipper mission. Credit: NASA/JPL

Since 1979, when the Voyager probes flew past Jupiter and its system of moons, scientists have speculated about the possibility of life within Europa. Based on planetary modeling, Europa is believed to be differentiated between a rocky and metallic core, an icy crust and mantle, and a liquid-water ocean that could be 100 to 200 km (62 to 124 mi) deep. Scientists theorize that this ocean is maintained by tidal flexing, where interaction with Jupiter’s powerful gravitational field leads to geological activity in Europa’s core and hydrothermal vents at the core-mantle boundary.

Investigating the potential habitability of Europa is the main purpose of NASA’s Europa Clipper mission, which will launch on October 10th, 2024, and arrive around Jupiter in April 2030. However, this presents a challenge for astrobiologists since the habitability of Europa is dependent on many interrelated parameters that require collaborative investigation. In a recent paper, a team of NASA-led researchers reviewed the objectives of the Europa Clipper mission and anticipated what it could reveal regarding the moon’s interior, composition, and geology.

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A Swarm Of Swimming Microbots Could Be Deployed To Europa’s Ocean

Europa and other ocean worlds in our solar system have recently attracted much attention. They are thought to be some of the most likely places in our solar system for life to have developed off Earth, given the presence of liquid water under their ice sheathes and our understanding of liquid water as one of the necessities for the development of life. Various missions are planned to these ocean worlds, but many suffer from numerous design constraints. Requirements to break through kilometers of ice on a world far from the Sun will do that to any mission. These design constraints sometimes make it difficult for the missions to achieve one of their most important functions – the search for life. But a team of engineers from NASA’s Jet Propulsion Laboratory think they have a solution – send forth a swarm of swimming microbots to scour the ocean beneath a main “mothership” bot.

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Four of Uranus’ Moons Might Have Liquid Oceans, Too

Recent computer models estimate the likelihood of interior oceans in four of Uranus’ major moons: Ariel, Umbriel, Titania, and Oberon, but Miranda is likely too small to sustain enough heat for an interior ocean. (Credit: NASA/JPL-Caltech)

The study of ocean worlds, planetary bodies with potential interior reservoirs of liquid water, has come to the forefront in terms of astrobiology and the search for life beyond Earth. From Jupiter’s Galilean Moons to Saturn’s Titan and Mimas to Neptune’s Triton and even Pluto, scientists are craving to better understand if these worlds truly possess interior bodies of liquid water. But what about Uranus and its more than two dozen moons? Could they harbor interior oceans, as well?

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Moons Orbiting Rogue Planets Could be Habitable

An artist's conception of a potentially-habitable exomoon. Credit: NASA

When looking for signs of life beyond the Solar System, astrobiologists are confined to looking for life as we understand it. For the most part, that means looking for rocky planets that orbit within their star’s circumsolar habitable zone (HZ), the distance at which liquid water can exist on its surface. In the coming years, next-generation telescopes and instruments will allow astronomers to characterize exoplanet atmospheres like never before. When that happens, they will look for the chemical signatures we associate with life, like nitrogen, oxygen, carbon dioxide, methane, and ammonia.

However, astrobiologists have theorized that life could exist in the outer Solar System beneath the surfaces of icy moons like Europa, Callisto, Titan, and other “Ocean Worlds.” Because of this, there is no shortage of astrobiologists who think that the search for extraterrestrial life should include exomoons, including those that orbit free-floating planets (FFPs). In a recent study, researchers led by the Max Planck Institute for Extraterrestrial Physics (MPE) determined the necessary properties that allow moons orbiting FFPs to retain enough liquid water to support life.

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Hubble and Spitzer Team up to Find a Pair of Waterworld Exoplanets

Artist’s impression of a water world, where half of its mass consists of water. Just like our Moon, the planet is bound to its star by tidal forces and always shows the same face to its host star. Credit: Pilar Montañés

As of December 19th, 2022, 5,227 extrasolar planets have been confirmed in 3,908 systems, with over 9,000 more awaiting confirmation. While most of these planets are Jupiter- or Neptune-sized gas giants or rocky planets many times the size of Earth (Super-Earths), a statistically significant number have been planets where water makes up a significant part of their mass fraction – aka. “water worlds.” These planets are unlike anything we’ve seen in the Solar System and raise several questions about planet formation in our galaxy.

In a recent study, an international team led by researchers from the University of Montreal’s Institute for Research on Exoplanets (iREx) found evidence of two water worlds in a single planetary system located about 218 light-years away in the constellation Lyra. Based on their densities, the team determined that these exoplanets (Kepler-138c and Kepler-138d) are lighter than rocky “Earth-like” ones but heavier than gas-dominated ones. The discovery was made using data from NASA’s now-retired Spitzer Space Telescope and the venerable Hubble Space Telescope.

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NASA has Built a Collection of Instruments That Will Search for Life Inside Europa and Enceladus

Counterclockwise from top: California’s Mono Lake was the site of a field test for JPL’s Ocean Worlds Life Surveyor. A suite of eight instruments designed to detect life in liquid samples from icy moons, OWLS can autonomously track lifelike movement in water flowing past its microscopes. Credit: NASA/JPL-Caltech

One of the most exciting aspects of space exploration today is how the field of astrobiology – the search for life in our Universe – has become so prominent. In the coming years, many robotic and even crewed missions will be bound for Mars that will aid in the ongoing search for life there. Beyond Mars, missions are planned for the outer Solar System that will explore satellites and bodies with icy exteriors and interior oceans – otherwise known as “Ocean Worlds.” These include the Jovian satellites Europa and Ganymede and Saturn’s moons Titan and Enceladus.

Similar to how missions to Mars have analyzed soil and rock samples for evidence of past life, the proposed missions will analyze liquid samples for the chemical signatures that we associate with life and biological processes (aka. “biosignatures”). To aid in this search, scientists at NASA’s Jet Propulsion Laboratory have designed the Ocean Worlds Life Surveyor (OWLS), a suite of eight scientific instruments designed to sniff out biosignatures. In the coming decades, this suite could be used by robotic probes bound for “Ocean Worlds” all across the Solar System to search for signs of life.

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A Swarm of Swimming Robots to Search for Life Under the Ice on Europa

An artist’s interpretation of liquid water on the surface of the Europa pooling beneath chaos terrain. Credit: : NASA/JPL-Caltech

When Galileo pointed his telescope at Jupiter 400 years ago, he saw three blobs of light around the giant planet, which he at first thought were fixed stars. He kept looking, and eventually, he spotted a fourth blob and noticed the blobs were moving. Galileo’s discovery of objects orbiting something other than Earth—which we call the Galilean moons in his honour—struck a blow to the Ptolemaic (geocentric) worldview of the time.

Galileo couldn’t have foreseen the age of space exploration that we’re living in now. Fast forward 400 years, and here we are. We know the Earth doesn’t occupy any central point. We’ve discovered thousands of other planets, and many of them will have their own moons. Galileo would be amazed at this.

What would he think about robotic missions to explore one of the blobs of light he spotted?

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