Would Mars be More Habitable if it Orbited a Red Dwarf?

Artist’s rendering of an exoplanet system experiencing atmospheric escape in connection with its host star. Credit: MACH Center / Aurore Simonnet

Thanks to the explosion in discoveries made in the last decade, the study of extrasolar planets have entered a new phase. With 4,884 confirmed discoveries in 3,659 systems (and another 7,958 candidates awaiting confirmation), scientists are shifting their focus from discovery to characterization. This means examining known exoplanets more closely to determine if they possess the necessary conditions for life, as well as “biomarkers” that could indicate the presence of life.

A key consideration is how the type of star may impact a planet’s chances of developing the right conditions for habitability. Consider red dwarf stars, the most common stellar class in the Universe and a great place to find “Earth-like,” rocky planets. According to a new study by an international team of scientists, a lifeless planet in our own backyard (Mars) might have evolved differently had it orbited a red dwarf instead of the Sun.

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Astronomers Measure the Atmosphere on a Planet Hundreds of Light-Years Away

The NASA/ESA Hubble Space Telescope’s data was used to analyze the atmosphere of the super-hot exoplanet WASP-79b, located 780 light-years away in the constellation Eridanus. Among exoplanets, WASP-79b is among the largest ever observed. The planet is larger than Jupiter, and its very deep, hazy atmosphere sizzles at 1,650 degrees Celsius – the temperature of molten glass. The Hubble Space Telescope and other observatories measured how starlight is filtered through the planet's atmosphere, allowing for its chemical composition to be analyzed. Hubble has detected the presence of water vapor. The surprise in recently published results, is that the planet's sky doesn't have any evidence for an atmospheric phenomenon called Rayleigh scattering, where certain colors of light are dispersed by very fine dust particles in the upper atmosphere. Rayleigh scattering is what makes Earth's skies blue by scattering the shorter (bluer) wavelengths of sunlight. Because WASP-79b doesn't seem to have this phenomenon, the daytime sky would likely be yellowish, researchers say. Link: NASA Press Release

The field of extrasolar planet research has advanced by leaps and bounds over the past fifteen years. To date, astronomers have relied on space-based and ground-based telescopes to confirm the existence of 4,566 exoplanets in 3,385 systems, with another 7,913 candidates awaiting confirmation. More importantly, in the past few years, the focus of exoplanet studies has slowly shifted from the process of discovery towards characterization.

In particular, astronomers are making great strides when it comes to the characterization of exoplanet atmospheres. Using the Gemini South Telescope (GST) in Chile, an international team led by Arizona State University (ASU) was able to characterize the atmosphere of a “hot Jupiter” located 340 light-years away. This makes them the first team to directly measure the chemical composition of a distant exoplanet’s atmosphere, a significant milestone in the hunt for habitable planets beyond our Solar System.

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Ocean Worlds With Hydrogen-Rich Atmospheres Could be the Perfect Spots for Life

Artist's impression of the surface of a "Hycean" world. Credit: University of Cambridge

The search for planets beyond our Solar System (extrasolar planets) has grown by leaps and bounds in the past decade. A total of 4,514 exoplanets have been confirmed in 3,346 planetary systems, with another 7,721 candidates awaiting confirmation. At present, astrobiologists are largely focused on the “low hanging fruit” approach of looking for exoplanets that are similar in size, mass, and atmospheric composition to Earth (aka. “Earth-like.”)

However, astrobiologists are also interested in finding examples of “exotic life,” the kind that emerged under conditions that are not “Earth-like.” For example, a team of astronomers from the University of Cambridge recently conducted a study that showed how life could emerge on ocean-covered planets with hydrogen-rich atmospheres (aka. “Hycean” planets). These findings could have significant implications for exoplanet studies and the field of astrobiology.

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How Would Rain be Different on an Alien World?

Artist’s impression of a sunset seen from the surface of an Earth-like exoplanet. Credit: ESO/L. Calçada

On Titan, Saturn’s largest moon, it rains on a regular basis. As with Earth, these rains are the result of liquid evaporating on the surface, condensing in the skies, and falling back to the surface as precipitation. On Earth, this is known as the hydrological (or water) cycle, which is an indispensable part of our climate. In Titan’s case, the same steps are all there, but it is methane that is being exchanged and not water.

In recent years, scientists have found evidence of similar patterns involving exoplanets, with everything from molten metal to lava rain! This raises the question of just how exotic the rains may be on alien worlds. Recently, a team of researchers from Havard University conducted a study where they researched how rain would differ in a diverse array of extrasolar planetary environments.

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What Role do Radioactive Elements Play in a Planet’s Habitability?

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)

To date, astronomers have confirmed the existence of 4,301 extrasolar planets in 3,192 star systems, with another 5,650 candidates awaiting confirmation. In the coming years, next-generation telescopes will allow astronomers to directly observe many of these exoplanets and place tighter constraints on their potential habitability. In time, this could lead to the discovery of life beyond our Solar System!

The only problem is, finding evidence of life requires that we know what to look for. According to a new study by an interdisciplinary team of scientists from the University of California Santa Cruz (UCSC), radioactive elements might play a role in planetary habitability. Future studies of rocky exoplanets, they argue, should therefore look for specific isotopes that indicate the presence of long-lived elements like thorium and uranium.

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Based on Kepler Data, There’s a 95% Chance of an Earth-Like Planet Within 20 Light-Years

Credit: NASA

In the past few decades, the study of exoplanets has grown by leaps and bounds, with 4296 confirmed discoveries in 3,188 systems and an additional 5,634 candidates awaiting confirmation. Because of this, scientists have been able to get a better idea about the number of potentially-habitable planets that could be out there. A popular target is stars like our own, which are known as G-type yellow dwarfs.

Recently, an international team of scientists (led by researchers from the NASA Ames Research Center) combined data from by the now-defunct Kepler Space Telescope and the European Space Agency’s (ESA) Gaia Observatory. What this revealed is that half of the Sun-like stars in our Universe could have rocky, potentially-habitable planets, the closest of which could be in our cosmic backyard!

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How Did the TRAPPIST-1 Planets Get Their Water?

Most exoplanets orbit red dwarf stars because they're the most plentiful stars. This is an artist's illustration of what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech
Most exoplanets orbit red dwarf stars because they're the most plentiful stars. This is an artist's illustration of what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech

In 2017, an international team of astronomers announced a momentous discovery. Based on years of observations, they found that the TRAPPIST-1 system (an M-type red dwarf located 40 light-years from Earth) contained no less than seven rocky planets! Equally exciting was the fact that three of these planets were found within the star’s Habitable Zone (HZ), and that the system itself has had 8 billion years to develop the chemistry for life.

At the same time, the fact that these planets orbit tightly around a red dwarf star has given rise to doubts that these three planets could maintain an atmosphere or liquid water for very long. According to new research by an international team of astronomers, it all comes down to the composition of the debris disk that the planets formed from and whether or not comets were around to distribute water afterward.

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Here’s What the Climate Might Look Like on Proxima Centauri B

Credit: NASA

Located at the heart of the NASA Center for Climate Simulation (NCCS) – part of NASA’s Goddard Space Flight Center – is the Discover supercomputer, a 129,000-core cluster of Linux-based processors. This supercomputer, which is capable of conducting 6.8 petaflops (6.8 trillion) operations per second, is tasked with running sophisticated climate models to predict what Earth’s climate will look like in the future.

However, the NCCS has also started to dedicate some of Discover’s supercomputing power to predict what conditions might be like on any of the over 4,000 planets that have been discovered beyond our Solar System. Not only have these simulations shown that many of these planets could be habitable, they are further evidence that our very notions of “habitability” could use a rethink.

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Complex Life Might Require a Very Narrow Habitable Zone

Kepler-452b
This artist's concept depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of star that is similar to our sun. Credit: NASA Ames/JPL-Caltech/T. Pyle

Since the Kepler Space Telescope was launched into space, the number of known planets beyond our Solar System (exoplanets) has grown exponentially. At present, 3,917 planets have been confirmed in 2,918 star systems, while 3,368 await confirmation. Of these, about 50 orbit within their star’s circumstellar habitable zone (aka. “Goldilocks Zone”) , the distance at which liquid water can exist on a planets’ surface.

However, recent research has raised the possibility that we consider to be a habitable zone is too optimistic. According to a new study that recently appeared online, titled “A Limited Habitable Zone for Complex Life“, habitable zones could be much narrower than originally thought. These finds could have a drastic impact on the number of planets scientists consider to be “potentially habitable”.

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Even if Exoplanets Have Atmospheres With Oxygen, it Doesn’t Mean There’s Life There

Artist’s impression of a sunset seen from the surface of an Earth-like exoplanet. Credit: ESO/L. Calçada

In their efforts to find evidence of life beyond our Solar System, scientists are forced to take what is known as the “low-hanging fruit” approach. Basically, this comes down to determining if planets could be “potentially habitable” based on whether or not they would be warm enough to have liquid water on their surfaces and dense atmospheres with enough oxygen.

This is a consequence of the fact that existing methods for examining distant planets are largely indirect and that Earth is only one planet we know of that is capable of supporting life. But what if planets that have plenty of oxygen are not guaranteed to produce life? According to a new study by a team from Johns Hopkins University, this may very well be the case.

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