ocean worlds Archives

September 7, 2024September 7, 2024 by Matt Williams

Could Comets have Delivered the Building Blocks of Life to “Ocean Worlds” like Europa, Enceladus, and Titan too?

The "ocean worlds" of the Solar System. Credit: NASA/JPL

Throughout Earth’s history, the planet’s surface has been regularly impacted by comets, meteors, and the occasional large asteroid. While these events were often destructive, sometimes to the point of triggering a mass extinction, they may have also played an important role in the emergence of life on Earth. This is especially true of the Hadean Era (ca. 4.1 to 3.8 billion years ago) and the Late Heavy Bombardment, when Earth and other planets in the inner Solar System were impacted by a disproportionately high number of asteroids and comets.

These impactors are thought to have been how water was delivered to the inner Solar System and possibly the building blocks of life. But what of the many icy bodies in the outer Solar System, the natural satellites that orbit gas giants and have liquid water oceans in their interiors (i.e., Europa, Enceladus, Titan, and others)? According to a recent study led by researchers from Johns Hopkins University, impact events on these “Ocean Worlds” could have significantly contributed to surface and subsurface chemistry that could have led to the emergence of life.

September 5, 2024September 9, 2024 by Matt Williams

Ouch! A Monster Asteroid Crashed Into Ganymede 4 Billion Years Ago, Rolling it Over

Artist's impression of the large impact that caused Ganymede to reorient itself 4 billion years ago. © HIRATA Naoyuki

Jupiter’s moon, Ganymede, is a fascinating celestial body. Measuring 5,268 km (3,272 mi) in diameter, it is also the largest satellite in the Solar System and even larger than Mercury, which measures 4,880 km (3,032 mi) in diameter. Like Europa, it has an interior ocean and is one of the few bodies in the Solar System (other than the gas giants) with an intrinsic magnetic field. The presence of this field also means Ganymede experiences aurorae circling the regions around its northern and southern poles due to interaction with Jupiter’s magnetic field.

In addition, based on its surface craters, scientists believe that Ganymede experienced a powerful impact with an asteroid about 4 billion years ago. This asteroid was about 20 times larger than the Chicxulub asteroid that caused the extinction of the dinosaurs, or the Cretaceous–Paleogene extinction event (ca. 66 million years ago). According to a recent study by Naoyuki Hirata of Kobe University, this impact occurred almost precisely on the meridian farthest away from Jupiter. This caused a reorientation of Ganymede’s rotational axis and allowed Hirata to determine exactly what type of impact took place.

May 30, 2024May 30, 2024 by Matt Williams

Pluto Has an Ocean of Liquid Water Surrounded by a 40-80 km Ice Shell

NASA's New Horizons spacecraft captured this image of Sputnik Planitia — a glacial expanse rich in nitrogen, carbon monoxide and methane ices — that forms the left lobe of a heart-shaped feature on Pluto’s surface. SwRI scientists studied the dwarf planet’s nitrogen and carbon monoxide composition to develop a new theory for its formation. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

On July 14th, 2015, the New Horizons spacecraft conducted the first-ever flyby of Pluto, which once was (and to many, still is) the ninth planet of the Solar System. While the encounter was brief, the stunning images and volumes of data it obtained revealed a stunningly vibrant and dynamic world. In addition to Pluto’s heart, floating ice hills, nitrogen icebergs, and nitrogen winds, the New Horizons data also hinted at the existence of an ocean beneath Pluto’s icy crust. This effectively made Pluto (and its largest moon, Charon) members of the “Ocean Worlds” club.

Almost a decade after that historic encounter, scientists are still making discoveries from New Horizons data. In a new paper, planetary scientists Alex Nguyen and Dr. Patrick McGovern used mathematical models and images to learn more about the possible ocean between Pluto’s icy surface and its silicate and metallic core. According to their analysis, they determined that Pluto’s ocean is located beneath a surface shell measuring 40 to 80 km (25 to 50 mi), an insulating layer thick enough to ensure that an interior ocean remains liquid.

March 13, 2024March 16, 2024 by Matt Williams

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.

February 13, 2024February 13, 2024 by Laurence Tognetti

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?

December 15, 2023December 16, 2023 by Evan Gough

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?

December 4, 2023December 4, 2023 by Matt Williams

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.

August 29, 2023August 29, 2023 by Andy Tomaswick

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.

May 18, 2023May 18, 2023 by Laurence Tognetti

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?

March 28, 2023March 28, 2023 by Matt Williams

Moons Orbiting Rogue Planets Could be Habitable

An artist's conception of a potentially-habitable exomoon. It seems reasonable that exoplanets have exomoons, and now we're going to look for them. 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.