The Heaviest Element Ever Seen in an Exoplanet’s Atmosphere: Barium

exoplanet hot jupiter transiting its star
This artist’s impression shows an ultra-hot exoplanet as it is about to transit in front of its host star. Credit: ESO

Astronomers have spotted barium in the atmosphere of a distant exoplanet. With its 56 protons, you have to run your finger further down the periodic table than astronomers usually do to find barium. What does finding such a heavy element in an exoplanet atmosphere mean?

It means we’re still learning how strange exoplanets can be.

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Scientists Discover a New Way Exoplanets Could Make Oxygen; Unfortunately, it Doesn’t Require Life

Oxygen is a valuable biosignature because Earth is oxygen-rich, and because life made all that oxygen. But if we find oxygen in an exoplanet atmosphere does that mean life made it? Or is there an abiotic source of oxygen? Image Credit: NASA

Finding oxygen in an exoplanet’s atmosphere is a clue that life may be at work. On Earth, photosynthetic organisms absorb carbon dioxide, sunlight, and water and produce sugars and starches for energy. Oxygen is the byproduct of that process, so if we can detect oxygen elsewhere, it’ll generate excitement. But researchers have also put pressure on the idea that oxygen in an exoplanet’s atmosphere indicates life. It’s only evidence of life if we can rule out other pathways that created the oxygen.

But scientists can’t rule them out.

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It’s Not Conclusive, But Methane is Probably the Best Sign of Life on Exoplanets

Illustration of Kepler-186f, a recently-discovered, possibly Earthlike exoplanet that could be a host to life. (NASA Ames, SETI Institute, JPL-Caltech, T. Pyle)

When the James Webb Space Telescope aims at exoplanet atmospheres, it’ll use spectroscopy to identify chemical elements. One of the things it’s looking for is methane, a chemical compound that can indicate the presence of life.

Methane is a compelling biosignature. Finding a large amount of methane in an exoplanet’s atmosphere might be our most reliable indication that life’s at work there. There are abiotic sources of methane, but for the most part, methane comes from life.

But to understand methane as a potential biosignature, we need to understand it in a planetary context. A new research letter aims to do that.

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The Building Blocks of Earth Could Have Come From Farther out in the Solar System

Artist's impression of the asteroid belt. Image credit: NASA/JPL-Caltech

Earth formed over 4.5 billion years ago via accretion. Earth’s building blocks were chunks of rock of varying sizes. From dust to planetesimals and everything in between. Many of those chunks of rock were carbonaceous meteorites, which scientists think came from asteroids in the outer reaches of the main asteroid belt.

But some evidence doesn’t line up well behind that conclusion. A new study says that some of the Earth-forming meteorites came from much further out in the Solar System.

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Even More Complex Organic Molecules Have Been Found in a Protoplanetary Disc. Was Life Inevitable?

This artist's concept a protoplanetary disk around a young star. Researchers at the Leiden Observatory found the large organic molecule dimethyl ether in a protoplanetary disk for the first time. Credit: NASA/JPL-Caltech

Will we ever understand life’s origins? Will we ever be able to put our finger on the exact moment and circumstances that lead to living matter? Will we ever pinpoint the spark? Who knows.

But what we can do is find out how widespread the conditions for life are and how widespread the molecular constituents for life are.

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What’s it Like Inside a Super-Earth?

This artist’s impression shows the planet orbiting the Sun-like star HD 85512 in the southern constellation of Vela (The Sail). This planet is one of sixteen super-Earths discovered by the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory. This planet is about 3.6 times as massive as the Earth lis at the edge of the habitable zone around the star, where liquid water, and perhaps even life, could potentially exist. Credit: ESO

We know a ton about the inside of Earth. We know it has both an inner core and an outer core and that the churning and rotation create a protective magnetosphere that shields life from the Sun’s radiative power. It has a mantle, primarily solid but also home to magma. We know it has a crust, where we live, and plate tectonics that moves the continents around like playthings.

But what about Super-Earths? We know they’re out there; we’ve found them. What do we know about their insides? Earth’s structure, and its ability to support life, are shaped by the extreme pressure and density in its interior. The pressure and temperature inside Super-Earths are even more powerful. How does it shape these planets and affect their habitability?

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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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Curiosity Sees a Strong Carbon Signature in a Bed of Rocks

This is the Stimson sandstone formation in Gale Crater on Mars. This is where the Curiosity Rover drilled the Edinburgh hole and found enriched Carbon 12. Image Credit: NASA/Caltech-JPL/MSSS

Carbon is critical to life, as far as we know. So anytime we detect a strong carbon signature somewhere like Mars, it could indicate biological activity.

Does a strong carbon signal in Martian rocks indicate biological processes of some type?

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Did Cosmic Dust Deliver the Phosphorus Needed for Life?

Sunlight reflects off tiny, interplanetary dust particles, creating the faint column of glowing light seen against the stars in this image. New research suggests that cosmic dust might be an important source of phosphorus for life on Earth. Credit: Malcol, CC BY 3.0

Without phosphorus, there’s no life. It’s a necessary part of DNA, RNA, and other biological molecules like ATP, which helps cells transport energy. But any phosphorus that was present when Earth formed would’ve been sequestered in the center of the molten planet.

So where did phosphorus come from?

It might have come from cosmic dust.

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How To Search the Chemical Makeup of Exoplanet Atmospheres for Hints at Their History

Author’s note – this article was written with Dr. Vincent Kofman, a scientist at NASA’s Goddard Space Flight Center (GSFC), working in the Sellers Exoplanet Environments Collaboration (SEEC), and the lead author on the research it discusses.

Thousands of exoplanets have been discovered in the recent decades. Planet hunters like TESS and Kepler, as well as numerous ground-based efforts, have pushed the field and we are starting to get a total number of planets that will allow us to perform effective statistical analysis on some of them.

Not only do the detected number of planets show us how common they are; it exposes our lack of understanding about how planets form, what conditions are present, and when planets may be habitable. The transit detection of an exoplanet primarily yields the orbital period, or the length of a year on the planet, and the relative size of the planet with respect to the star. The next steps are to characterize the planet. This usually requires follow up studies, using different observational strategies and more powerful telescopes.

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