Linking Organic Molecules to Hydrothermal Vents on Enceladus

Saturn's moon Enceladus isn't just bright and beautiful. It has an ocean under all that ice that could have hydrothermal vents that create organic chemicals. Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team

Despite the vast distance between us and Saturn’s gleaming moon Enceladus, the icy ocean moon is a prime target in our search for life. It vents water vapour and large organic molecules into space through fissures in its icy shell, which is relatively thin compared to other icy ocean moons like Jupiter’s Europa. Though still out of reach, scientific access to its ocean is not as challenging as on Europa, which has a much thicker ice shell.

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A Single Grain of Ice Could Hold Evidence of Life on Europa and Enceladus

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

The Solar System’s icy ocean moons are primary targets in our search for life. Missions to Europa and Enceladus will explore these moons from orbit, improving our understanding of them and their potential to support life. Both worlds emit plumes of water from their internal oceans, and the spacecraft sent to both worlds will examine those plumes and even sample them.

New research suggests that evidence of life in the moons’ oceans could be present in just a single grain of ice, and our spacecraft can detect it.

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Venus’ Clouds Contain Sulfuric Acid. That’s Not a Problem for Life.

Photo of Venus (Credit: Akatsuki)

A recent study published in Astrobiology investigates the potential habitability in the clouds of Venus, specifically how amino acids, which are the building blocks of life, could survive in the sulfuric acid-rich upper atmosphere of Venus. This comes as the potential for life in Venus’ clouds has become a focal point of contention within the astrobiology community in the last few years. On Earth, concentrated sulfuric acid is known for its corrosivity towards metals and rocks and for absorbing water vapor. In Venus’ upper atmosphere, it forms from solar radiation interacting with sulfur dioxide, water vapor, and carbon dioxide.

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Toxic Gas is Leaking out of Enceladus. It’s also a Building Block of Life.

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

Enceladus’ status as a target in the search for life keeps rising. We’ve known for years that plumes erupting from the ocean under the moon’s icy shell contain important organic compounds related to life. Now, researchers have found another chemical in the plumes which is not only highly toxic but also critical in the appearance of life.

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Under Some Conditions, Comets Could Deliver Organic Molecules to Planets

This artwork shows a rocky planet being bombarded by comets. Image credit: NASA/JPL-Caltech

Approximately 4.1 to 3.8 billion years ago, the planets of the inner Solar System experienced many impacts from comets and asteroids that originated in the outer Solar System. This is known as the Late Heavy Bombardment (LHB) period when (according to theory) the migration of the giant planets kicked asteroids and comets out of their regular orbits, sending them hurtling towards Mercury, Venus, Earth, and Mars. This bombardment is believed to have distributed water to the inner Solar System and maybe the building blocks of life itself.

According to new research from the University of Cambridge, comets must travel slowly – below 15 km/s (9.32 mi/s) – to deliver organic material onto other planets. Otherwise, the essential molecules would not survive the high speed and temperatures generated by atmospheric entry and impact. As the researchers found, such comets are only likely to occur in tightly bound systems where planets orbit closely to each other. Their results show that these systems would be a good place to look for evidence of life (biosignatures) beyond the Solar System.

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Another Key Amino Acid Found in Space: Tryptophan

Tryptophan found in the nebula IC348. Credit: Jorge Rebolo-Iglesias/NASA/Spitzer Space Telescope

Astrochemistry is the study of how molecules can form and react in space. Its roots trace back to the 1800s when astronomers such as William Wollaston and Joseph von Fraunhofer began identifying atomic elements from the spectral lines of the Sun. But it wasn’t until recent decades that the field began to mature.

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How Could We Detect Life Inside Enceladus?

Scientists recently determined that a certain strain of Earth bacteria could thrive under conditions found on Enceladus. Credit: NASA/JPL/Space Science Institute

For astrobiologists, the scientists dedicated to the search for life beyond Earth, the moons of Saturn are a virtual treasure trove of possibilities. Enceladus is especially compelling because of the active plumes of water emanating from its southern polar region. Not only are these vents thought to be connected directly to an ocean beneath the moon’s icy surface, but the Cassini mission detected traces of organic molecules and other chemicals associated with biological processes. Like Europa, Ganymede, and other “Ocean Worlds,” astrobiologists think this could indicate hydrothermal activity at the core-mantle boundary.

Both NASA and the ESA are hoping to send missions to Enceladus that could study its plumes in more detail. These include the Enceladus Orbitlander recommended in the Planetary Science and Astrobiology Decadal Survey 2023-2032 and the ESA’s Enceladus Moonraker, which could depart Earth in the next decade, taking advantage of a favorable alignment between the planets. In anticipation of what these missions could find, an international team of researchers used data from the Cassini mission to establish how samples of plume material could constrain how much biomass Enceladus has within it.

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Meteorites Bathed in Gamma Rays Produce More Amino Acids and Could Have Helped Life get Going on Earth

Carbonaceous chondrites like the Allende meteorite contain significant amounts of water and amino acids. Could they have delivered amino acids to early Earth and spurred on the development of life? Image Credit: By Shiny Things - originally posted to Flickr as AMNH - Meteorite, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=4196153

Our modern telescopes are more powerful than their predecessors, and our research is more focused than ever. We keep discovering new things about the Solar System and finding answers to long-standing questions. But one of the big questions we still don’t have an answer for is: ‘How did life on Earth begin?’

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Samples of Asteroid Ryugu Contain More Than 20 Amino Acids

Artist's impression of the Hayabusa2 spacecraft touching down on the surface of the asteroid Ryugu. Credit: JAXA/Akihiro Ikeshita?

In 2014, the Japan Aerospace Exploration Agency (JAXA) dispatched its Hayabusa2 spacecraft to rendezvous with 162173 Ryugu, a Near-Earth Asteroid (NEA) that periodically passes close to Earth. In 2018, this sample-return mission reached Ryugu and spent the next year and a half studying its surface and obtaining samples from its surface and subsurface. By 2020, these samples made it back to Earth, where scientists began analyzing them in the hopes of learning more about the early history of the Solar System and answering key questions about the origins of life.

Earlier this year, the first results of the analysis showed that Ryugu is (as expected) rich in carbon, organic molecules, and volatiles (like water) and hinted at the possibility that it was once a comet. Based on a more recent analysis, eight teams of Japanese researchers (including one from JAXA) recently announced that Ryugu carries strains of no less than 20 different amino acids -the building blocks of DNA and life itself! These findings could provide new insight into how life is distributed throughout the cosmos and could mean that it is more common than previously thought.

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One of Life’s Building Blocks can Form in Space

A new kind of chemical reaction can explain how peptides can form on the icy layers of cosmic dust grains. Those peptides could have been transported to the early Earth by meteorites, asteroids or comets. Image Credit: © S. Krasnokutski / MPIA Graphics Department

Peptides are one of the smallest biomolecules and are one of life’s critical building blocks. New research shows that they could form on the surfaces of icy grains in space. This discovery lends credence to the idea that meteoroids, asteroids, or comets could have given life on Earth a kick start by crashing into the planet and delivering biological building blocks.

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