Planet Nine: Theories About the Hypothetical Planet

Artist's illustration of Planet Nine, a hypothesized world about 10 times more massive than Earth that may orbit in the far outer solar system. Doomsayers’ fears about the putative planet are unfounded, experts stress.

A massive ice giant may be traveling through the outer solar system. Dubbed "Planet Nine," the hypothetical world was proposed to exist after scientists noticed that a handful of objects beyond Pluto had been shaken up in unusual orbits. Search parties have formed to find the unseen planet, with optimistic hopes of spotting it within a year.

"It's not crazy; this is the kind of stuff people are finding all the time," co-discoverer Mike Brown, at the California Institute of Technology, told Space.com earlier this year. Brown and lead author Konstantin Batygin, also at CalTech, published a paper in January 2016 suggesting that a massive planet could be stirring up the icy bodies of the Kuiper Belt, a ring of material at the edge of the solar system.

"We just need to go out and cover a good swath of the sky." 

An unseen planet

Pluto makes its home at the edge of the Kuiper Belt, a region of ice-covered rocks left over from the formation of the solar system. Batygin and Brown noticed that several of the objects had similarities in their orbits, which suggested they were affected by a massive body. The usual suspects would be the solar system’s giant planets, but the objects the pair spotted were too far away to be affected by the behemoths.

By analyzing the strange orbits of the objects, Batygin and Brown proposed the presence of a new planet in the solar system, an object four times as large as Earth and 10 times as massive. They traced the possible orbit of the unseen giant, which they called "Planet Nine." To create the observed disturbances, they mapped an orbit that comes as close as 200 astronomical units (AU) from the sun and travel as far away as 1,200 AU. (One AU is the distance from Earth to the sun — about 93 million miles, or 150 million kilometers.)

Not everyone is convinced that an enormous giant is skulking around the edges of the solar system. Ann-Marie Madigan, a postdoctoral researcher at the University of California Berkeley, found that the objects could "self-organize," pushing and pulling one another into their unusual orbits. Working with co-author Michael McCourt of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, the pair found that if the objects in the scattered disk roughly equal the mass of Earth, they could have dragged themselves to their current orbits within about 600 million years of the solar system’s birth, omitting the need for Planet Nine’s interference.

According to Batygin and Brown, however, the Planet Nine scenario is more probable, because current surveys suggest there isn’t enough mass in the region. In their research, they note that the disk of material that birthed the planets may have started out with enough mass, but interactions with the giant planets would have quickly tossed it out of the solar system.

Another study suggested that Planet Nine could be tugging on NASA’s Cassini probe, orbiting Saturn. Agnès Fienga at the Côte d'Azur Observatory in France and her colleagues added Planet Nine to a theoretical model to see if the proposed world could solve the mystery of tiny changes in the spacecraft’s orbit that existing solar system objects cannot account for. If the missing planet lies about 600 AUs away toward the constellation Cetus, the puzzling perturbations can be accounted for.
According to Cassini’s mission managers, however, the spacecraft isn’t actually experiencing any mysterious anomalies.

"Although we'd love it if Cassini could help detect a new planet in the solar system, we do not see any perturbations in our orbit that we cannot explain with our current models," said Earl Maize, Cassini project manager at JPL, in a statement.

Other objects in the Kuiper Belt may help nail down the case for the world. Research by Renu Halhotra, Kathryn Volk and Xianyu Wang, all at the University of Arizona, reveal half a dozen ice-cover rocks whose orbits appear to fit with the presence of a distant planet.

"It’s a different line of evidence than Mike Brown and Konstantin Batygin proposed,"

"I think it’s really intriguing."

The possible internal structure of Planet Nine, a large world hypothesized to exist far beyond the orbit of Pluto.

Where did it come from?

A planet in the outer solar system today has to come from somewhere. Without directly seeing it, scientists can only model possibilities for the massive world. 

One possibility is that the sun somehow managed to gravitationally grab onto a free-floating world or a planet orbiting another star and add it to the solar system’s crown. Computer simulations performed by Gongjie Li and Fred Adams, both of the CfA, suggest that the odds of this happening are less than 2 percent.

If Planet Nine didn’t come from outside the solar system, then it must have come from within. Models performed by Scott Kenyon of the CfA and Benjamin Bromely of the University of Utah suggest there’s a good chance the hypothetical world could have been born where it was, or been booted into the outer solar system by interactions with the giant planets.

"The nice thing about these scenarios is that they’re observationally testable," Kenyon said in a statement.

"A scattered gas giant will look like a cold Neptune, while a planet that formed in place will resemble a giant Pluto with no gas."

Not everyone is waiting to see the planet before trying to dive inside of it. Astrophysics professor Christoph Mordasini and his doctoral student Esther Linder, both of the University of Bern in Switzerland, modeled what astronomers might see when they spot Planet Nine. 

Assuming that it is a smaller version of the ice giants Uranus and Neptune, with hydrogen and helium dominating its atmosphere, the pair calculated that a 10-Earth-mass Planet Nine would be about 3.7 times wider than our planet. Temperatures would average minus 375 degrees Fahrenheit (minus 226 degrees Celsius).

"This means that the planet’s emission is dominated by the cooling of its core," Linder said in a statement.

Sunlight would contribute very little to the light of the planet, making it brighter in the infrared wavelengths than in visible light.

Although the world remains unseen, that doesn’t mean we should fear it. Reports by the New York Post published in April claimed that Planet Nine could hurl asteroids and comets toward Earth, with potentially devastating consequences. The video, which had several factual errors, was dismissed by Brown.

He also dismissed the idea that the world played a role in mass extinctions of the past. While the planet orbits a significant distance from the sun, it isn’t quite far enough out to stir up the Oort Cloud, the region of icy comets beyond the Kuiper Belt. With a 10,000-year orbit, it would also constantly bombard the Earth, Brown said.

Hunting the unseen

Planet Nine remains hypothetical; no one has actually seen the world. But that doesn’t mean scientists aren’t searching for it. Batygin and Brown started off by searching through previous skymaps, hunting their unseen world.

"We dumpster-dived into the existing observational data to search for Planet Nine," Batygin said." Because we didn’t find it we were able to rule out parts of its orbit."

Exoplanet researcher Nicolas Cowan of McGill University in Montreal thinks Planet Nine might show up in present and future surveys of the cosmic microwave background. Depending on the planet’s orbit, it could also be picked up by the Dark Energy Survey, a project in the Southern Hemisphere designed to probe the acceleration of the universe. NASA’s WISE instrument should also be able to spot the giant, helping to narrow down the potential paths of the planet.

Linder and Mordasini remain cautious. According to their models, existing surveys would likely be incapable of spotting the world if it weighs in at less than 20 Earth masses, especially if it was far enough away.

Batygin and Brown are trying to obtain telescope time on the Subaru Telescope on Mauna Kea in Hawaii. They’re asking for roughly 20 nights of observing, a significant amount of time on a powerful instrument that is constantly in use.
"It’s a pretty big request compared to what other people generally get on the telescope,"

"We’ll see if they bite."

If they do, he estimated that the planet could be spotted within a year.

Astronomers discover planet with three suns

An artist's impression of the triple-star system HD 131399 from close to the giant planet orbiting in the system.

Astronomers have found a strange world where the seasons last longer than a human lifetime. In some seasons it is always light, while in others there are three sunrises and sunsets a day.

The planet, HD 131399Ab, is a gas giant, 340 light-years from Earth in the constellation Centaurus and is a part of a complex three-star system, called HD 131399.

Two of the stars are binary system while HD 131399Ab orbits the third, brighter star in the widest known orbit within a multi-star system.
The planet is massive about four times Jupiter’s mass with a temperature of 850 kelvin (580 °C).

But, at only about 16 million years old, it is it one of the youngest exoplanets discovered so far.

“HD 131399Ab is one of the few exoplanets that have been directly imaged, and it’s the first one in such an interesting dynamical configuration,” said Daniel Apai of the University of Arizona.

His team observed the system using direct imaging at ESO's Very Large Telescope (VLT) in Chile as part of the Nexus for Exoplanet System Science (NExSS) project, dedicated to the search for life on planets outside our solar system.


The system appears to be centred on a star about 80% more massive than the sun, which itself is orbited by the two remaining stars, denominated B and C, at about 300 AU (one AU, or astronomical unit, equals the average distance between Earth and the sun).

B and C twirl around each other like a spinning dumbbell, separated by a distance roughly equal to that between our sun and Saturn.

Planet HD 131399Ab travels around the central star, A, in an orbit about twice as large as Pluto’s in our solar system.

“For about half of the planet’s orbit, which lasts 550 Earth-years, three stars are visible in the sky, the fainter two always much closer together, and changing in apparent separation from the brightest star throughout the year”

“For much of the planet’s year, the stars appear close together, giving it a familiar night-side and day-side with a unique triple-sunset and sunrise each day.

“As the planet orbits and the stars grow farther apart each day, they reach a point where the setting of one coincides with the rising of the other at which point the planet is in near-constant daytime for about one-quarter of its orbit, or roughly 140 Earth-years.”

HD 131399Ab is the first exoplanet to be discovered with SPHERE – the Spectro-Polarimetric High-Contrast Exoplanet Research Instrument installed on the VLT.

SPHERE is sensitive to infrared light, making it capable of detecting the heat signatures of young planets, along with sophisticated features correcting for atmospheric disturbances and blocking out the otherwise blinding light of their host stars.

NASA Probe Arrives at Jupiter After 5-Year Trek

NASA's robotic Juno probe began circling the solar system's largest planettonight (July 4), ending a nearly five-year journey through deep space and becoming the first spacecraft to enter Jupiter orbit since NASA's Galileo mission did so in 1995.

The milestone came late tonight, as Juno fired its main engine in a crucial 35-minute burn that slowed the probe down enough to be captured by Jupiter's powerful gravity. That burn started at 11:18 p.m. EDT (0318 GMT Tuesday) and ended on schedule at 11:53 p.m.

In the hours leading up to the engine burn, that same gravity had accelerated Juno to an estimated 165,000 mph (265,000 km/h) relative to Earth — faster than any human-made object has ever traveled, mission team members have said.

Tonight's orbit-insertion burn, which Juno performed on autopilot, was a make-or-break maneuver: If anything had gone seriously wrong, Juno would have gone sailing right past Jupiter, and the science goals of the $1.1 billion mission — which including mapping the planet's gravitational and magnetic fields and characterizing its composition and interior structure — would have gone unaccomplished.

So the jubilation that erupted at Juno mission control here at NASA's Jet Propulsion Laboratory (JPL) — shouts of joy, high-fiving and hugging among team members — made a lot of sense.

"Welcome to Jupiter!" a mission commentator announced just after the burn ended, eliciting a second round of cheers and then, a few moments later, a standing ovation.

"It feels great — this is phenomenal!" Geoff Yoder, acting Associate Administrator for NASA's Science Mission Directorate, said when the celebration died down.

Record-setting journey

Juno launched in August 2011 and took a circuitous route through the solar system, looping back to make a speed-boosting flyby of Earth in October 2013.

Juno notched more than just the all-time speed record during its long trek. This past January, the probe became the farthest-flung solar-powered spacecraft in history, zooming past the record of 492 million miles (792 million kilometers) from the sun, which had been held by the European Space Agency's comet-chasing Rosetta mission.

Jupiter lies five times farther from the sun than Earth does, and as a result receives 25 times less sunlight than our home planet gets. To harness that meager supply, Juno sports a total of 18,698 individual solar cells, which are spread among three 29.5-foot-long (9 meters) panels.

With these panels extended, Juno is about the size of a basketball court.
Gathering enough energy to operate is far from the only challenge Juno faces at Jupiter. For example, the area around the giant planet is the most intense radiation environment in the solar system, mission team members have said.
Jupiter's magnetic field, which is 20,000 times stronger than that of Earth, accelerates huge swarms of electrons to nearly the speed of light.

"Once these electrons hit a spacecraft, they immediately begin to ricochet and release energy, creating secondary photons and particles, which then ricochet," Heidi Becker, leader of Juno’s radiation-monitoring team, said during a news conference on June 16. "It's like a spray of radiation bullets." 

Juno's flight computer and other sensitive electronics are encased by a 400-lb. (180 kilograms) titanium vault to protect them against this barrage. The spacecraft's scientific instruments also wear what Becker called "bulletproof vests," as does the star-tracking camera Juno uses for navigation.

Such precautions are necessary when dealing with the king of planets, which is so big that all of the other bodies in the solar system except the sun — all the planets, dwarf planets, comets and asteroids — could fit inside it.

"Jupiter is a planet on steroids," Juno principal investigator Scott Bolton, of the Southwest Research Institute in San Antonio, said during the same news conference. "Everything about it is extreme."

What Is the Big Bang Theory?

A 2013 map of the background radiation left over from the Big Bang, taken by the ESA's Planck spacecraft, captured the oldest light in the universe. This information helps astronomers determine the age of the universe.

The Big Bang Theory is the leading explanation about how the universe began. At its simplest, it talks about the universe as we know it starting with a small singularity, then inflating over the next 13.8 billion years to the cosmos that we know today.

Because current instruments don't allow astronomers to peer back at the universe's birth, much of what we understand about the Big Bang Theory comes from mathematical theory and models. Astronomers can, however, see the "echo" of the expansion through a phenomenon known as the cosmic microwave background.

The phrase "Big Bang Theory" has been popular among astrophysicists for decades, but it hit the mainstream in 2007 when a comedy show with the same name premiered on CBS. The show follows the home and academic life of several researchers (including an astrophysicist).

The first second, and the birth of light

In the first second after the universe began, the surrounding temperature was about 10 billion degrees Fahrenheit (5.5 billion Celsius), according to NASA. The cosmos contained a vast array of fundamental particles such as neutrons, electrons and protons. These decayed or combined as the universe got cooler.

This early soup would have been impossible to look at, because light could not carry inside of it. "The free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds," NASA stated. Over time, however, the free electrons met up with nuclei and created neutral atoms. This allowed light to shine through about 380,000 years after the Big Bang.

This early light — sometimes called the "afterglow" of the Big Bang — is more properly known as the cosmic microwave background (CMB). It was first predicted by Ralph Alpher and other scientists in 1948, but was found only by accident almost 20 years later.

Arno Penzias and Robert Wilson, both of Bell Telephone Laboratories in Murray Hill, New Jersey, were building a radio receiver in 1965 and picking up higher-than-expected temperatures, according to NASA. At first, they thought the anomaly was due to pigeons and their dung, but even after cleaning up the mess and killing pigeons that tried to roost inside the antenna, the anomaly persisted.

Simultaneously, a Princeton University team (led by Robert Dicke) was trying to find evidence of the CMB, and realized that Penzias and Wilson had stumbled upon it. The teams each published papers in the Astrophysical Journal in 1965.

Determining the age of the universe

The cosmic microwave background has been observed on many missions. One of the most famous space-faring missions was NASA's Cosmic Background Explorer (COBE) satellite, which mapped the sky in the 1990s.

Several other missions have followed in COBE's footsteps, such as the BOOMERanG experiment (Balloon Observations of Millimetric Extragalactic Radiation and Geophysics), NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the European Space Agency's Planck satellite.

Planck's observations, released in 2013, mapped the background in unprecedented detail and revealed that the universe was older than previously thought: 13.82 billion years old, rather than 13.7 billion years old. [Related: How Old is the Universe?]
The maps give rise to new mysteries, however, such as why the Southern Hemisphere appears slightly redder (warmer) than the Northern Hemisphere. The Big Bang Theory says that the CMB would be mostly the same, no matter where you look.

Examining the CMB also gives astronomers clues as to the composition of the universe. Researchers think most of the cosmos is made up of matter and energy that cannot be "sensed" with conventional instruments, leading to the names dark matter and dark energy. Only 5 percent of the universe is made up of matter such as planets, stars and galaxies.

This graphic shows a timeline of the universe based on the Big Bang theory and inflation models.

Gravitational waves controversy

While astronomers could see the universe's beginnings, they've also been seeking out proof of its rapid inflation. Theory says that in the first second after the universe was born, our cosmos ballooned faster than the speed of light. That, by the way, does not violate Albert Einstein's speed limit since he said that light is the maximum anything can travel within the universe. That did not apply to the inflation of the universe itself.

In 2014, astronomers said they had found evidence in the CMB concerning "B-modes," a sort of polarization generated as the universe got bigger and created gravitational waves. The team spotted evidence of this using an Antarctic telescope called "Background Imaging of Cosmic Extragalactic Polarization", or BICEP2.

"We're very confident that the signal that we're seeing is real, and it's on the sky," lead researcher John Kovac, of the Harvard-Smithsonian Center for Astrophysics, told Space.com in March 2014.

But by June, the same team said that their findings could have been altered by galactic dust getting in the way of their field of view.

"The basic takeaway has not changed; we have high confidence in our results," Kovac said in a press conference reported by the New York Times. "New information from Planck makes it look like pre-Planckian predictions of dust were too low," he added.
The results from Planck were put online in pre-published form in September. By January 2015, researchers from both teams working together "confirmed that the Bicep signal was mostly, if not all, stardust,"

Faster inflation, multiverses and charting the start

The universe is not only expanding, but getting faster as it inflates. This means that with time, nobody will be able to spot other galaxies from Earth, or any other vantage point within our galaxy.

"We will see distant galaxies moving away from us, but their speed is increasing with time," Harvard University astronomer Avi Loeb said in a March 2014 Space.com article.

"So, if you wait long enough, eventually, a distant galaxy will reach the speed of light. What that means is that even light won't be able to bridge the gap that's being opened between that galaxy and us. There's no way for extraterrestrials on that galaxy to communicate with us, to send any signals that will reach us, once their galaxy is moving faster than light relative to us."

Some physicists also suggest that the universe we experience is just one of many. In the "multiverse" model, different universes would coexist with each other like bubbles lying side by side. The theory suggests that in that first big push of inflation, different parts of space-time grew at different rates. This could have carved off different sections — different universes — with potentially different laws of physics.

"It's hard to build models of inflation that don't lead to a multiverse," Alan Guth, a theoretical physicist at the Massachusetts Institute of Technology, said during a news conference in March 2014 concerning the gravitational waves discovery. 

"It's not impossible, so I think there's still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking [the idea of a] multiverse seriously."

While we can understand how the universe we see came to be, it's possible that the Big Bang was not the first inflationary period the universe experienced. Some scientists believe we live in a cosmos that goes through regular cycles of inflation and deflation, and that we just happen to be living in one of these phases

Mysterious 'Dark Hydrogen' May Lurk Within Giant Planets

Laboratory experiments suggest that a layer of "dark hydrogen" lies between the atmospheres and cores of Jupiter and other gas giants.

Exotic "dark hydrogen" lurks within giant planets such as Saturn and Jupiter, a new study suggests.

This strange form of hydrogen likely lies between the gaseous hydrogen in the clouds of gas giants such as Saturn and Jupiter and the liquid-metal hydrogen found in these planets' cores, according to the study.

"This dark hydrogen layer was unexpected and inconsistent with what modeling research had led us to believe about the change from hydrogen gas to metallic hydrogen inside of celestial objects," co-author Alexander Goncharov, a physicist at the Carnegie Institution for Science in Washington, D.C., said in a statement.
Goncharov and his colleagues used a laser-heated "diamond anvil cell" to create the conditions likely to be found inside gas giants. Probing hydrogen under pressures ranging from 10,000 to 1.5 million times that found in Earth's atmosphere, and through temperatures as high as 10,000 degrees Fahrenheit (5,500 degrees Celsius), they discovered an intermediate phase of the element.

Jupiter, Saturn, Neptune and Uranus all have gaseous hydrogen atmospheres that extend all the way to their mantles. A layer of liquid metal hydrogen lies within their cores. Dark hydrogen may separate the boundary in between, the researchers said.
Dark hydrogen is so named because it doesn’t transmit or reflect visible light. However, the stuff does transmit infrared radiation.

"This observation would explain how heat can easily escape from gas giants like Saturn," Goncharov said.

Dark hydrogen is slightly metallic and can conduct an electric current (though not as well as liquid-metal hydrogen does). The material likely plays a role in creating magnetic fields around the planets of the outer solar system, the researchers said.

Silicate Stardust Traces Histories of Dust in the Galaxy

NASA scientists are revealing the histories of dust particles from dying stars that roved the Galaxy for millions of years before the sun and planets formed. These stardust grains survived the harsh environment of deep space and were found in meteorites on Earth.

During their journeys, these stardust grains were bombarded in space by high-energy cosmic radiation and shock waves from exploding stars, or supernovae. Scientists in the Astromaterials Research and Exploration Science Division at NASA’s Johnson Space Center in Houston used state-of-the-art instrumentation to study the histories of these ancient silicate stardust grains.

 A paper on the team’s findings has been published in The Astrophysical Journal.
The coordinated laboratory study of these remnants of stars that were once light years away from us has revealed detailed information on the conditions in stellar atmospheres and in the Galaxy. “These tiny stardust grains reveal incredible details of their parent stars, their journey through the Galaxy and the earliest history of the Solar System. Astrophysics in the laboratory is a powerful complement to the traditional means of studying the cosmos with telescopes,” said co-author Scott Messenger, NASA senior astromaterials and mission scientist.

The isotope signatures and atomic-scale structures were determined for individual grains of stardust that are smaller than 1/1000 of a millimeter in size. The small size of these grains makes these coordinated analyses especially challenging.
The silicate stardust grains were discovered by measuring their exotic isotopic compositions with the use of a high spatial resolution ion probe known as the NanoSIMS 50L. The isotopic compositions of stardust grains were imparted by nuclear reactions deep within the hearts of their parent stars and can be orders of magnitude different from the compositions of grains that formed in the Solar System. In particular, the abundance ratios of different isotopes of oxygen in silicate stardust are diagnostic of the type of star from which they came.

“About 1 in every 5,000 silicate grains from the meteorites we studied was produced by another star before our Solar System formed. After analyzing millions of silicate grains, we identified bona fide silicate stardust from three major dust producers in the Galaxy: red giant stars, explosive supernovae, and novae,” said the leading author, Dr. Ann Nguyen, Jacobs cosmochemist at NASA’s Johnson Space Center.
“The next step was to determine the chemistry and structure of these grains in order to answer questions such as, under what conditions did these grains form? How different were these conditions in stellar outflows compared to more violent stellar explosions? What types of environments did the grains encounter on their journey to our Solar System?”

These questions were addressed by carefully producing cross-sections of 9 silicate stardust grains. These cross-sections were a mere ~70 nanometers thick and were analyzed by co-author Lindsay Keller using another powerful instrument, the transmission electron microscope, or TEM.

“Coordinated analyses of these grains is a powerful approach. The isotopic measurements reveal that these grains originated from very different types of stars. Combining this information with the TEM observations provides us with unique insights into the physical and chemical conditions that existed when the grains formed,” said Keller, NASA planetary scientist.

Many of the silicates were amorphous with a wide range of chemical compositions. The study also uncovered silicate crystals from red giants that likely formed at higher temperatures than the amorphous grains.

Evidence for radiation processing in space was found in two of the stardust grains studied, one from a red giant star and one from a supernova. Both of the grains have the same chemical composition consistent with the mineral enstatite. One grain is completely amorphous while the other retains a crystalline core.

These transmission electron microscope (TEM) images reveal that one interstellar grain consists of a small crystalline enstatite core within a non-crystalline (amorphous) silicate of similar elemental composition. The ‘bright field’ TEM image on the left shows density contrast, where the thick dark rind surrounding the interstellar grain (circled in red) is a protective platinum strap used for sample preparation. In the ‘dark field’ TEM image on the right, crystalline materials appear bright and amorphous materials are dark. The scale bar is 50 nanometers in length, 50 billionths of a meter.

"The chemical composition of the grains indicates they originally formed as crystals, but these grains later encountered high energy radiation in space sufficient to destroy their crystal structures. Evidence of this radiation exposure is extremely rare in silicate stardust. Most of the stardust grains that we studied seem to have escaped such processing,”

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Scientists Discover Unexpected Mineral on Mars

This low-angle self-portrait of NASA's Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin."

Scientists have discovered an unexpected mineral in a rock sample at Gale Crater on Mars, a finding that may alter our understanding of how the planet evolved.

NASA’s Mars Science Laboratory rover, Curiosity, has been exploring sedimentary rocks within Gale Crater since landing in August 2012. On sol 1060 (the number of Martian days since landing), the rover collected powder drilled from rock at a location named “Buckskin.” Analyzing data from an X-ray diffraction instrument on the rover that identifies minerals, scientists detected significant amounts of a silica mineral called tridymite.

This detection was a surprise to the scientists, because tridymite is generally associated with silicic volcanism, which is known on Earth but was not thought to be important or even present on Mars. Tridymite requires high temperatures and high silica concentrations to form, conditions which most typically are found in association with silicic volcanism.

The discovery of tridymite might induce scientists to rethink the volcanic history of Mars, suggesting that the planet once had explosive volcanoes that led to the presence of the mineral.

Scientists in the Astromaterials Research and Exploration Science (ARES) Division at NASA’s Johnson Space Center in Houston led the study. A paper on the team’s findings has been published in the Proceedings of the National Academy of Sciences.
“On Earth, tridymite is formed at high temperatures in an explosive process called silicic volcanism. Mount St. Helens, the active volcano in Washington State, and the Satsuma-Iwojima volcano in Japan are examples of such volcanoes. The combination of high silica content and extremely high temperatures in the volcanoes creates tridymite,” said Richard Morris, NASA planetary scientist at Johnson and lead author of the paper. “The tridymite was incorporated into ‘Lake Gale’ mudstone at Buckskin as sediment from erosion of silicic volcanic rocks.”

The paper also will stimulate scientists to re-examine the way tridymite forms. The authors examined terrestrial evidence that tridymite could form at low temperatures from geologically reasonable processes and not imply silicic volcanism. They found none. Researchers will need to look for ways that it could form at lower temperatures.
“I always tell fellow planetary scientists to expect the unexpected on Mars,” said Doug Ming, ARES chief scientist at Johnson and co-author of the paper. “The discovery of tridymite was completely unexpected. This discovery now begs the question of whether Mars experienced a much more violent and explosive volcanic history during the early evolution of the planet than previously thought.”

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