NASA’s Galileo spacecraft captured this image of a volcanic eruption on Io in 1997. Image Credit:NASA, NASA-JPL, DLR
Jupiter’s moon Io is the most volcanically active body in the Solar System, with roughly 400 active volcanoes regularly ejecting magma into space. This activity arises from Io’s eccentric orbit around Jupiter, which produces incredibly powerful tidal interactions in the interior. In addition to powering Io’s volcanism, this tidal energy is believed to support a global subsurface magma ocean. However, the extent and depth of this ocean remains the subject of debate, with some supporting the idea of a shallow magma ocean while others believe Io has a more rigid, mostly solid interior.
In a recent NASA-supported study, an international team of researchers combined data from multiple missions to measure Io’s tidal deformation. According to their findings, Io does not possess a magma ocean and likely has a mostly solid mantle. Their findings further suggest that tidal forces do not necessarily lead to global magma oceans on moons or planetary bodies. This could have implications for the study of exoplanets that experience tidal heating, including Super-Earths and exomoons similar to Io that orbit massive gas giants.
Infrared satellite image (10.4 ?m) taken by Himawari-8 for the last reported event on January 14
Volcanoes are not restricted to the land, there are many undersea versions. One such undersea volcano known as Hunga Tonga-Hunga Ha’apai off the coast of Tonga. On 15th January 2022, it underwent an eruption which was one of the most powerful in recent memory. A recent paper shows that seismic waves were released 15 minutes before the eruption and before any visible disruption at the surface. The waves had been detected by a seismic station 750km away. This is the first time a precursor signal has been detected.
The Lafayette Meteorite was chipped off the surface of Mars and then sped through space for roughly 11 million years. It eventually found its way into a drawer at Purdue University in 1931 and has since been teaching scientists about Mars. (Photo provided by Purdue Brand Studio.)
11 million years ago, Mars was a frigid, dry, dead world, just like it is now. Something slammed into the unfortunate planet, sending debris into space. A piece of that debris made it to Earth, found its way into a drawer at Purdue University, and then was subsequently forgotten about.
Until 1931, when scientists studied and realized it came directly from Mars. What has it told them about the red planet?
NASA’s Juno spacecraft was sent to Jupiter to study the gas giant. But its mission was extended, giving it an opportunity to study the unique moon Io. Io is the most volcanically active body in the Solar System, with over 400 active volcanoes.
Researchers have taken advantage of Juno’s flybys of Io to study how tidal heating affects the moon.
Artist's concept of InSight "taking the pulse of Mars". Credit: NASA/JPL-Caltech
Since February 2019, NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander has been making the first-ever measurements of tectonics on another planet. The key to this is InSight’s Seismic Experiment for Interior Structure (SEIS) instrument (developed by seismologists and geophysicists at ETH Zurich), which has been on the surface listening for signs of “marsquakes.” The dataset it has gathered (over 1,300 seismic events) has largely confirmed what planetary scientists have long suspected: that Mars is largely quiet.
However, a research team led by ETH Zurich recently analyzed a cluster of more than 20 recent marsquakes, which revealed something very interesting. Based on the location and spectral character of these events, they determined that most of Mars’ widely distributed surface faults are not seismically active. Nevertheless, most of the 20 seismic events observed originated in the vicinity of Cerberus Fossae, a region consisting of rifts (or graben). These results suggest that geological activity and volcanism still play an active role in shaping the Martian surface.
This artist's illustration shows what an icy exo-Earth might look like. A new study says liquid water could persist under ice sheets on planets outside of their habitable zones. Image Credit: NASA
Hundreds of millions of years ago, Earth went through two episodes of severe glaciation. These two episodes—the Sturtian and the Marinoan glaciations—occured during the Earth’s Cryogenian Period. The Cryogenian lasted from about 720 million to 635 million years ago.
The phenomenon is called “Snowball Earth” and both instances of it happened in pretty quick succession. And while a planet encased in ice and snow sounds devastating, these episodes may have paved the way for the development of complex life.
The question is, what caused the Earth to freeze over like that?
We intend to explore the Moon, use its resources, and use it as a jumping-off point for missions deeper into the Solar System. For that we need a Lunar GPS. Image Credit: NASA
The Moon is easily the most well-studied object in the Solar System, (other than Earth, of course.) But it still holds some puzzles for scientists. Why, for instance, is one side of the Moon so different from the other?
Artist's conception of a terraformed Venus, showing a surface largely covered in oceans. Credit: Wikipedia Commons/Ittiz
In 1978, NASA’s Pioneer Venus (aka. Pioneer 12) mission reached Venus (“Earth’s Sister”) and found indications that Venus may have once had oceans on its surface. Since then, several missions have been sent to Venus and gathered data on its surface and atmosphere. From this, a picture has emerged of how Venus made the transition from being an “Earth-like” planet to the hot and hellish place it is today.
It all started about 700 million years ago when a massive resurfacing event triggered a runaway Greenhouse Effect that caused Venus’s atmosphere to become incredibly dense and hot. This means that for 2 to 3 billion years after Venus formed, the planet could have maintained a habitable environment. According to a recent study, that would have been long enough for life to have emerged on “Earth’s Sister”.
Artist's concept of Kepler-69c, a super-Earth-size planet in the habitable zone of a star like our sun, located about 2,700 light-years from Earth in the constellation Cygnus. Credit: NASA
When looking for potentially-habitable extra-solar planets, scientists are somewhat restricted by the fact that we know of only one planet where life exists (i.e. Earth). For this reason, scientists look for planets that are terrestrial (i.e. rocky), orbit within their star’s habitable zones, and show signs of biosignatures such as atmospheric carbon dioxide – which is essential to life as we know it.
This gas, which is the largely result of volcanic activity here on Earth, increases surface heat through the greenhouse effect and cycles between the subsurface and the atmosphere through natural processes. For this reason, scientists have long believed that plate tectonics are essential to habitability. However, according to a new study by a team from Pennsylvania State University, this may not be the case.
The study, titled “Carbon Cycling and Habitability of Earth-Sized Stagnant Lid Planets“, was recently published in the scientific journal Astrobiology. The study was conducted by Bradford J. Foley and Andrew J. Smye, two assistant professors from the department of geosciences at Pennsylvania State University.
The Earth’s Tectonic Plates. Credit: msnucleus.org
On Earth, volcanism is the result of plate tectonics and occurs where two plates collide. This causes subduction, where one plate is pushed beneath the other and deeper into the subsurface. This subduction changes the dense mantle into buoyant magma, which rises through the crust to the Earth’s surface and creates volcanoes. This process can also aid in carbon cycling by pushing carbon into the mantle.
Plate tectonics and volcanism are believe to have been central to the emergence of life here on Earth, as it ensured that our planet had sufficient heat to maintain liquid water on its surface. To test this theory, Professors Foley and Smye created models to determine how habitable an Earth-like planet would be without the presence of plate tectonics.
These models took into account the thermal evolution, crustal production and CO2 cycling to constrain the habitability of rocky, Earth-sized stagnant lid planets. These are planets where the crust consists of a single, giant spherical plate floating on mantle, rather than in separate pieces. Such planets are thought to be far more common than planets that experience plate tectonics, as no planets beyond Earth have been confirmed to have tectonic plates yet. As Prof. Foley explained in a Penn State News press release:
“Volcanism releases gases into the atmosphere, and then through weathering, carbon dioxide is pulled from the atmosphere and sequestered into surface rocks and sediment. Balancing those two processes keeps carbon dioxide at a certain level in the atmosphere, which is really important for whether the climate stays temperate and suitable for life.”
Map of the Earth showing fault lines (blue) and zones of volcanic activity (red). Credit: zmescience.com
Essentially, their models took into account how much heat a stagnant lid planet’s climate could retain based on the amount of heat and heat-producing elements present when the planet formed (aka. its initial heat budget). On Earth, these elements include uranium which produces thorium and heat when it decays, which then decays to produce potassium and heat.
After running hundreds of simulations, which varied the planet’s size and chemical composition, they found that stagnant lid planets would be able to maintain warm enough temperatures that liquid water could exist on their surfaces for billions of years. In extreme cases, they could sustain life-supporting temperatures for up to 4 billion years, which is almost the age of the Earth.
As Smye indicated, this is due in part to the fact that plate tectonics are not always necessary for volcanic activity:
“You still have volcanism on stagnant lid planets, but it’s much shorter lived than on planets with plate tectonics because there isn’t as much cycling. Volcanoes result in a succession of lava flows, which are buried like layers of a cake over time. Rocks and sediment heat up more the deeper they are buried.”
Image of the Sarychev volcano (in Russia’s Kuril Islands) caught during an early stage of eruption on June 12, 2009. Taken by astronauts aboard the International Space Station. Credit: NASA
The researchers also found that without plate tectonics, stagnant lid planets could still have enough heat and pressure to experience degassing, where carbon dioxide gas can escape from rocks and make its way to the surface. On Earth, Smye said, the same process occurs with water in subduction fault zones. This process increases based on the quantity of heat-producing elements present in the planet. As Foley explained:
“There’s a sweet spot range where a planet is releasing enough carbon dioxide to keep the planet from freezing over, but not so much that the weathering can’t pull carbon dioxide out of the atmosphere and keep the climate temperate.”
According to the researchers’ model, the presence and amount of heat-producing elements were far better indicators for a planet’s potential to sustain life. Based on their simulations, they found that the initial composition or size of a planet is very important for determining whether or not it will become habitable. Or as they put it, the potential habitability of a planet is determined at birth.
By demonstrating that stagnant lid planets could still support life, this study has the potential for greatly extending the range of what scientists consider to be potentially-habitable. When the James Webb Space Telescope (JWST) is deployed in 2021, examining the atmospheres of stagnant lid planets to determine the presence of biosignatures (like CO2) will be a major scientific objective.
Knowing that more of these worlds could sustain life is certainly good news for those who are hoping that we find evidence of extra-terrestrial life in our lifetimes.
Image of the Sarychev volcano (in Russia's Kuril Islands) caught during an early stage of eruption on June 12, 2009. Taken by astronauts aboard the
International Space Station. Credit: NASA
Whenever the existence of an extra-solar planet is confirmed, there is reason to celebrate. With every new discovery, humanity increases the odds of finding life somewhere else in the Universe. And even if that life is not advanced enough (or particularly inclined) to build a radio antenna so we might be able to hear from them, even the possibility of life beyond our Solar System is exciting.
Unfortunately, determining whether or not a planet is habitable is difficult and subject to a lot of guesswork. While astronomers use various techniques to put constraints on the size, mass, and composition of extra-solar planets, there is no surefire way to know if these worlds are habitable. But according to a new study from a team of astronomers from Cornell University, looking for signs of volcanic activity could help.
Their study – titled “A Volcanic Hydrogen Habitable Zone” – was recently published in The Astrophysical Journal Letters. According to their findings, the key to zeroing in on life on other planets is to look for the telltale signs of volcanic eruptions – namely, hydrogen gas (H²). The reason being is that this, and the traditional greenhouse gases, could extend the habitable zones of stars considerably.
The habitable zones of three stars detected by the Kepler mission. Credit: NASA/Ames/JPL-Caltech
As Ramses Ramirez, a research associate at Cornell’s Carl Sagan Institute and the lead author of the study, said in a University press release:
“On frozen planets, any potential life would be buried under layers of ice, which would make it really hard to spot with telescopes. But if the surface is warm enough – thanks to volcanic hydrogen and atmospheric warming – you could have life on the surface, generating a slew of detectable signatures.”
Planetary scientists theorize that billions of years ago, Earth’s early atmosphere had an abundant supply of hydrogen gas (H²) due to volcanic outgassing. Interaction between hydrogen and nitrogen molecules in this atmosphere are believed to have kept the Earth warm long enough for life to develop. However, over the next few million years, this hydrogen gas escaped into space.
This is believed to be the fate of all terrestrial planets, which can only hold onto their planet-warming hydrogen for so long. But according to the new study, volcanic activity could change this. As long as they are active, and their activity is intense enough, even planets that are far from their stars could experience a greenhouse effect that would be sufficient to keep their surfaces warm.
Distant exoplanets that are not in the traditional “Goldilocks Zone” might be habitable, assuming they have enough volcanic activity. Credit: ESO.
Consider the Solar System. When accounting for the traditional greenhouse effect caused by nitrogen gas (N²), carbon dioxide and water, the outer edge of our Sun’s habitable zone extends to a distance of about 1.7 AU – just outside the orbit of Mars. Beyond this, the condensation and scattering of CO² molecules make a greenhouse effect negligible.
However, if one factors in the outgassing of sufficient levels of H², that habitable zone can extend that outer edge to about 2.4 AUs. At this distance, planets that are the same distance from the Sun as the Asteroid Belt would theoretically be able to sustain life – provided enough volcanic activity was present. This is certainly exciting news, especially in light of the recent announcement of seven exoplanets orbiting the nearby TRAPPIST-1 star.
Of these planets, three are believed to orbit within the star’s habitable zone. But as Lisa Kaltenegger – also a member of the Carl Sagan Institute and the co-author on the paper – indicated, their research could add another planet to this
“potentially-habitable” lineup:
“Finding multiple planets in the habitable zone of their host star is a great discovery because it means that there can be even more potentially habitable planets per star than we thought. Finding more rocky planets in the habitable zone – per star – increases our odds of finding life… Although uncertainties with the orbit of the outermost Trappist-1 planet ‘h’ means that we’ll have to wait and see on that one.”
Artist’s concept of the TRAPPIST-1 star system, an ultra-cool dwarf that has seven Earth-size planets orbiting it. Credits: NASA/JPL-Caltech
Another upside of this study is that the presence of volcanically-produced hydrogen gas would be easy to detect by both ground-based and space-based telescopes (which routinely conduct spectroscopic surveys on distant exoplanets). So not only would volcanic activity increase the likelihood of there being life on a planet, it would also be relatively easy to confirm.
“We just increased the width of the habitable zone by about half, adding a lot more planets to our ‘search here’ target list,” said Ramirez. “Adding hydrogen to the air of an exoplanet is a good thing if you’re an astronomer trying to observe potential life from a telescope or a space mission. It increases your signal, making it easier to spot the makeup of the atmosphere as compared to planets without hydrogen.”
Already, missions like Spitzer and the Hubble Space Telescope are used to study exoplanets for signs of hydrogen and helium – mainly to determine if they are gas giants or rocky planets. But by looking for hydrogen gas along with other biosignatures (i.e. methane and ozone), next-generation instruments like the James Webb Space Telescope or the European Extremely Large Telescope, could narrow the search for life.
It is, of course, far too soon to say if this study will help in our search for extra-solar life. But in the coming years, we may find ourselves one step closer to resolving that troublesome Fermi Paradox!
