HOTTEST
Any Martians out there should learn to duck and cover.
On May 4, the Red Planet was rocked by a roughly magnitude 5 temblor, the largest Marsquake detected to date, NASA’s Jet Propulsion Laboratory in Pasadena, Calif., reports. The shaking lasted for more than six hours and released more than 10 times the energy of the previous record-holding quake.
The U.S. space agency’s InSight lander, which has been studying Mars’ deep interior since touching down on the planet in 2018 (SN: 11/26/18), recorded the event. The quake probably originated near the Cerberus Fossae region, which is more than 1,000 kilometers from the lander.
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Cerberus Fossae is known for its fractured surface and frequent rockfalls. It makes sense that the ground would be shifting there, says geophysicist Philippe Lognonné, principal investigator of the Seismic Experiment for Interior Structure, InSight’s seismometer. “It’s an ancient volcanic bulge.”
Just like earthquakes reveal information about our planet’s interior structure, Marsquakes can be used to probe what lies beneath Mars’ surface (SN: 7/22/21). And a lot can be learned from studying this whopper of a quake, says Lognonné, of the Institut de Physique du Globe de Paris. “The signal is so good, we’ll be able to work on the details.” More
If every mineral tells a story, then geologists now have their equivalent of The Arabian Nights.
For the first time, scientists have cataloged every different way that every known mineral can form and put all of that information in one place. This collection of mineral origin stories hints that Earth could have harbored life earlier than previously thought, quantifies the importance of water as the most transformative ingredient in geology, and may change how researchers look for signs of life and water on other planets.
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“This is just going to be an explosion,” says Robert Hazen, a mineralogist and astrobiologist at the Carnegie Institution for Science in Washington, D.C. “You can ask a thousand questions now that we couldn’t have answered before.”
For over 100 years, scientists have defined minerals in terms of “what,” focusing on their structure and chemical makeup. But that can make for an incomplete picture. For example, though all diamonds are a kind of crystalline carbon, three different diamonds might tell three different stories, Hazen says. One could have formed 5 billion years ago in a distant star, another may have been born in a meteorite impact, and a third could have been baked deep below the Earth’s crust.
Diamonds have the same carbon structure, but they can form in different ways. This particular gem originated deep within the Earth.Rob Lavinsky/ARKENSTONE
So Hazen and his colleagues set out to define a different approach to mineral classification. This new angle focuses on the “how” by thinking about minerals as things that evolve out of the history of life, Earth and the solar system, he and his team report July 1 in a pair of studies in American Mineralogist. The researchers defined 57 main ways that the “mineral kingdom” forms, with options ranging from condensation out of the space between stars to formation in the excrement of bats.
The information in the catalog isn’t new, but it was previously scattered throughout thousands of scientific papers. The “audacity” of their work, Hazen says, was to go through and compile it all together for the more than 5,600 known types of minerals. That makes the catalog a one-stop shop for those who want to use minerals to understand the past.
The compilation also allowed the team to take a step back and think about mineral evolution from a broader perspective. Patterns immediately popped out. One of the new studies shows that over half of all known mineral kinds form in ways that ought to have been possible on the newborn Earth. The implication: Of all the geologic environments that scientists have considered as potential crucibles for the beginning of life on Earth, most could have existed as early as 4.3 billion years ago (SN: 9/24/20). Life, therefore, may have formed almost as soon as Earth did, or at the very least, had more time to arise than scientists have thought. Rocks with traces of life date to only 3.4 billion years ago (SN: 7/26/21).
“That would be a very, very profound implication — that the potential for life is baked in at the very beginning of a planet,” says Zachary Adam, a paleobiologist at the University of Wisconsin–Madison who was not involved in the new studies.
The exact timing of when conditions ripe for life arose is based on “iffy” models, though, says Frances Westall, a geobiologist at the Center for Molecular Biophysics in Orléans, France, who was also not part of Hazen’s team. She thinks that scientists need more data before they can be sure. But, she says, “the principle is fantastic.”
The new results also show how essential water has been to making most of the minerals on Earth. Roughly 80 percent of known mineral types need H2O to form, the team reports.
“Water is just incredibly important,” Hazen says, adding that the estimate is conservative. “It may be closer to 90 percent.”
Some minerals would not form in certain ways without the influence of life. Photosynthesizing bacteria helped bring about the oxygen-rich conditions needed for this azurite (left), while the opalized ammonite (right) was created by the mineral opal filling the space where an ammonite shell used to be.Rob Lavinsky/ARKENSTONE
Taken one way, this means that if researchers see water on a planet like Mars, they can guess that it has a rich mineral ecosystem (SN: 3/16/21). But flipping this idea may be more useful: Scientists could identify what minerals are on the Red Planet and then use the new catalog to work backward and figure out what its environment was like in the past. A group of minerals, for example, might be explainable only if there had been water, or even life.
Right now, scientists do this sort of detective work on just a few minerals at a time (SN: 5/11/20). But if researchers want to make the most of the samples collected on other planets, something more comprehensive is needed, Adam says, like the new study’s framework.
And that’s just the beginning. “The value of this [catalog] is that it’s ongoing and potentially multigenerational,” Adam says. “We can go back to it again and again and again for different kinds of questions.”
“I think we have a lot more we can do,” agrees Shaunna Morrison, a mineralogist at the Carnegie Institution and coauthor of the new studies. “We’re just scratching the surface.” More
THE WOODLANDS, TEXAS — Vestiges of a moon-forming cataclysm could have kick-started plate tectonics on Earth.
The leading explanation for the origin of the moon proposes that a Mars-sized planet, dubbed Theia, struck the nascent Earth, ejecting a cloud of debris into space that later coalesced into a satellite (SN: 3/2/18). New computer simulations suggest that purported remains of Theia deep inside the planet could have also triggered the onset of subduction, a hallmark of modern plate tectonics, geodynamicist Qian Yuan of Caltech reported March 13 at the Lunar and Planetary Science Conference.
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The story offers a cohesive explanation for how Earth gained both its moon and its moving tectonic plates, and it could aid in the search for other Earthlike worlds. But others caution that it’s much too early to say that this is, in fact, what happened.
Of all the worlds yet discovered, ours is the only one confirmed to have plate tectonics (SN: 1/13/21). For billions of years, Earth’s creeping plates have spread, collided and plunged beneath one another, birthing and splitting continents, uplifting mountain ranges and widening oceans (SN: 4/22/20, SN: 1/11/17). But all this reshaping has also erased most of the clues to the planet’s early history, including how and when plate tectonics first began.
Many hypotheses have been proposed to explain the initiation of subduction, a tectonic process in which one plate slides under another (SN: 5/2/22; SN: 6/5/19; SN: 1/2/18). Yuan and his colleagues chose to focus on two continent-sized blobs of material in Earth’s lower mantle known as large low-shear velocity provinces (SN: 5/12/16). These are regions through which seismic waves are known to move anomalously slow. Researchers had previously proposed these regions could have formed from old, subducted plates. But in 2021, Yuan and colleagues alternatively proposed that the mysterious masses could be the dense, sunken remnants of Theia.
Building off that previous work, the researchers used computers to simulate how Theia’s impact, and its lingering remains, would impact the flow of rock inside the Earth.
They found that once these hot alien blobs had sunk to the bottom of the mantle, they could have compelled large plumes of warm rock to upwell and wedge into Earth’s rigid outer layer. As upwelling continued to feed into the risen plumes, they would have ballooned and pushed slabs of Earth’s surface beneath them, triggering subduction about 200 million years after the moon formed.
While the simulations suggest the large low-shear velocity provinces could have had a hand in starting subduction, it’s not yet clear whether these masses came from Theia. “The features … are a fairly recent discovery,” says geodynamicist Laurent Montési of the University of Maryland in College Park. “They’re very fascinating structures, with a very unknown origin.” As such, he says, it’s too early to say that Theia triggered plate tectonics.
“It’s provoking. This material down there is something special,” Montési says of the large low-shear velocity provinces. “But whether it has to be originally extraterrestrial, I don’t think the case is made.”
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However, if confirmed, the explanation could have implications that reach beyond our solar system. “If you have a large moon, you likely have a large impactor,” Yuan said. Scientists have yet to confirm the discovery of such an exomoon (SN: 4/30/19). But keeping an eye out, Yuan said, could help us uncover another world as tectonically active as our own. More
The sun has set on the iconic Arecibo telescope.
Since 1963, this behemoth radio telescope in Puerto Rico has observed everything from space rocks whizzing past Earth to mysterious blasts of radio waves from distant galaxies. But on December 1, the 900-metric-ton platform of scientific instruments above the dish came crashing down, demolishing the telescope and spelling the end of Arecibo’s observing days.
Arecibo has made too many discoveries to include in a Top 10 list, so some of its greatest hits didn’t make the cut — like a strange class of stars that appear to turn on and off (SN: 1/6/17), and ingredients for life in a distant galaxy. But in honor of Arecibo’s 57-year tenure as one of the world’s premier observatories, here are 10 of the telescope’s coolest accomplishments, presented in roughly reverse order of coolness.
10. Clocking the Crab Nebula pulsar
Astronomers originally thought that apparently blinking stars called pulsars, discovered in 1967, might be pulsating white dwarf stars (SN: 4/27/68). But in 1968, Arecibo saw the pulsar at the center of the Crab Nebula flashing every 33 milliseconds — faster than white dwarfs can pulsate. (SN: 12/7/68). That discovery strengthened the idea that pulsars are actually rapidly spinning neutron stars, stellar corpses that sweep beams of radio waves around in space like celestial lighthouses (SN: 1/3/20).
Arecibo observations of the frequency of radio flashes from the pulsar at the center of the Crab Nebula (red star in the middle) gave support to the idea that pulsars are rapidly spinning neutron stars.Optical: NASA, HST, ASU, J. Hester et al.; X-ray: NASA, CXC, ASU, J. Hester et al.
9. Reborn pulsars
In 1982, Arecibo clocked a pulsar, dubbed PSR 1937+21, flashing every 1.6 milliseconds, unseating the Crab Nebula neutron star as the fastest known pulsar (SN: 12/4/82). That find was puzzling at first because PSR 1937+21 is older than the Crab Nebula pulsar, and pulsars were thought to rotate more slowly with age.
Then, astronomers realized that old pulsars can “spin-up” by siphoning mass from a companion star, and flash every one to 10 milliseconds. The NANOGrav project now uses such rapid-fire radio beacons as extremely precise cosmic clocks to search for the ripples in spacetime known as gravitational waves (SN: 2/11/16).
Pulsars typically rotate more slowly as they age. But data from Arecibo showed that pulsars can ‘spin-up’ to rotate hundreds of times per second by siphoning material off a neighboring star (as seen in this artist’s impression; pulsar in blue).ESA, Francesco Ferraro/Bologna Astronomical Observatory
8. Ice on Mercury
Mercury seems like it would be an unlikely place to find water ice because the planet is so close to the sun. But Arecibo observations in the early 1990s hinted that ice lurked in permanently shadowed craters at Mercury’s poles (SN: 11/9/91). NASA’s MESSENGER spacecraft later confirmed those observations (SN: 11/30/12). Finding ice on Mercury raised the question of whether ice might exist in shadowed craters on the moon, too — and recent spacecraft observations indicate that it does (SN: 5/9/16).
Images of Mercury taken by NASA’s MESSENGER spacecraft in 2011 and 2012 confirmed that hints of water ice (yellow) seen on the planet by Arecibo reside in shadowy regions at Mercury’s poles (north pole, shown; two craters labeled).NASA, JHUAPL, Carnegie Institution of Washington, Arecibo Observatory
7. Unveiling Venus
Venus is shrouded in a thick layer of clouds, but Arecibo’s radar beams could cut through that haze and bounce off of the rocky planet’s surface, allowing researchers to map the terrain. In the 1970s, Arecibo’s radar vision got the first large-scale views of Venus’ surface (SN: 11/3/79). Its radar images revealed evidence of past tectonic and volcanic activity on the planet, such as ridges and valleys (SN: 4/22/89) and ancient lava flows (SN: 9/18/76).Arecibo provided this early view of Venus’ surface using radar in 1971.D.B. Campbell/Cornell University
Technological advances have allowed Arecibo to get crisper views of Venus. This 2015 image showcases the planet’s northern hemisphere.Smithsonian Institution, NASA GFSC, Arecibo Observatory, NAIC6. Mercury’s revolution
In 1965, Arecibo radar measurements revealed that Mercury spins on its axis once every 59 days, rather than every 88 days (SN: 5/1/65). That observation cleared up a long-standing mystery about the planet’s temperature. If Mercury had turned on its axis once every 88 days, as previously thought, then the same side of the planet would always face the sun. That’s because it also takes 88 days for the planet to complete one orbit around the sun.
As a result, that side would be much hotter than the planet’s dark side. The 59-day rotation better matched the observation that Mercury’s temperature is fairly even across its surface.
Arecibo’s early radar observations measured the 59-day rotation rate of Mercury (shown in this false-color image of MESSENGER spacecraft data, which highlights chemical and mineralogical features on the planet’s surface).NASA, JHUAPL, Carnegie Institution of Washington
5. Mapping asteroids
Arecibo has cataloged the features of many near-Earth asteroids (SN: 5/7/10). In 1989, the observatory created a radar image of the asteroid 4769 Castalia, revealing the first double-lobed rock known in the solar system (SN: 11/25/89). Arecibo has since found space rocks orbiting each other in pairs (SN: 10/29/03) and trios (SN: 7/17/08).
Other odd finds have included a space rock whose shadows made it look to Arecibo like a skull, and an asteroid with the improbable shape of a dog bone (SN: 7/24/01). Understanding the characteristics and motion of near-Earth asteroids helps determine which ones might pose a danger to Earth — and how they could be safely deflected.
Arecibo radar images in 2000 revealed the strange dog bone shape of an asteroid named 216 Kleopatra (shown from multiple angles).WSU, NAIC, JPL/NASA
4. Phoning E.T.
The Arecibo Observatory broadcast the first radio message intended for an alien audience in November 1974 (SN: 11/23/74). That famous message was the most powerful signal ever sent from Earth, meant in part to demonstrate the capabilities of the observatory’s new high-power radio transmitter.
The message, beamed toward a cluster of about 300,000 stars roughly 25,000 light-years away, consisted of 1,679 bits of information. That string of binary code detailed the chemical formulas for components of DNA, a stick figure sketch of a human, a schematic of the solar system and other scientific data.3. Repeating radio blasts
Fast radio bursts, or FRBs, are brief, brilliant blasts of radio waves with unknown origins. The first FRB known to give off multiple bursts was FRB 121102, which Arecibo first spotted in 2012 and again in 2015 (SN: 3/2/16). Finding a repeating FRB ruled out the possibility that these bursts were generated by one-off cataclysmic events, such as stellar collisions. And because FRB 121102 kept recurring, astronomers were able to trace it back to its home: a dwarf galaxy about 2.5 billion light-years away (SN: 1/4/17). This confirmed the decade-long suspicion that FRBs come from beyond the Milky Way.
A repeating source of radio waves discovered by Arecibo (radio image, left) was the first fast radio burst traced back to its home galaxy. The burst originated in a dwarf galaxy about 2.5 billion light-years away (visible light image, right).H. Falcke/Nature 2017
2. Making waves
Gravitational waves were first directly detected in 2015 (SN: 2/11/16), but astronomers saw the first indirect evidence of ripples in spacetime decades ago. That evidence came from the first pulsar found orbiting another star, PSR 1913+16, first sighted by Arecibo in 1974 (SN: 10/19/74).
By tracking the arrival time of radio bursts from that pulsar over several years, astronomers were able to map its orbit, and found that PSR 1913+16 was spiraling toward its companion. As the orbits of the two stars contract, the binary system loses energy at the rate that would be expected if they were whipping up gravitational waves (SN: 2/24/79). This indirect observation of gravitational waves won the 1993 Nobel Prize in physics (SN: 10/23/93).
The first pulsar found orbiting another star, sighted by Arecibo in 1974, provided indirect evidence for the existence of ripples in spacetime called gravitational waves (illustrated).ESO, L. Calçada
1. Pulsar planets
The first planets discovered around another star were three small, rocky worlds orbiting the pulsar PSR B1257+12 (SN: 1/11/92). The find was somewhat serendipitous. In 1990, Arecibo was being repaired, and so it was stuck staring at one spot on the sky. During its observations, Earth’s rotation swept PSR B1257+12 across the telescope’s field of view. Small fluctuations in the arrival time of radio bursts from the pulsar indicated that the star was wobbling as a result of the gravitational tug of unseen planets (SN: 3/5/94).
Thousands of exoplanets have since been discovered orbiting other stars, including sunlike stars (SN: 10/8/19). Recent exoplanet surveys, however, suggest that pulsar-orbiting planets are rare (SN: 9/3/15).
The first worlds ever spotted beyond the solar system were three rocky planets (seen in this artist’s illustration) orbiting the pulsar PSR B1257+12.NASA, JPL-Caltech, R. Hurt/SSC MoreSEATTLE — Luke Skywalker’s home planet in Star Wars is the stuff of science fiction. But Tatooine-like planets in orbit around pairs of stars might be our best bet in the search for habitable planets beyond our solar system.
Many stars in the universe come in pairs. And lots of those should have planets orbiting them (SN: 10/25/21). That means there could be many more planets orbiting around binaries than around solitary stars like ours. But until now, no one had a clear idea about whether those planets’ environments could be conducive to life. New computer simulations suggest that, in many cases, life could imitate art.
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Earthlike planets orbiting some configurations of binary stars can stay in stable orbits for at least a billion years, researchers reported January 11 at the American Astronomical Society meeting. That sort of stability, the researchers propose, would be enough to potentially allow life to develop, provided the planets aren’t too hot or cold.
Of the planets that stuck around, about 15 percent stayed in their habitable zone — a temperate region around their stars where water could stay liquid — most or even all of the time.
The researchers ran simulations of 4,000 configurations of binary stars, each with an Earthlike planet in orbit around them. The team varied things like the relative masses of the stars, the sizes and shapes of the stars’ orbits around each other, and the size of the planet’s orbit around the binary pair.
The scientists then tracked the motion of the planets for up to a billion years of simulated time to see if the planets would stay in orbit over the sorts of timescales that might allow life to emerge.
A planet orbiting binary stars can get kicked out of the star system due to complicated interactions between the planet and stars. In the new study, the researchers found that, for planets with large orbits around star pairs, only about 1 out of 8 were kicked out of the system. The rest were stable enough to continue to orbit for the full billion years. About 1 in 10 settled in their habitable zones and stayed there.
Of the 4,000 planets that the team simulated, roughly 500 maintained stable orbits that kept them in their habitable zones at least 80 percent of the time.
“The habitable zone . . . as I’ve characterized it so far, spans from freezing to boiling,” said Michael Pedowitz, an undergraduate student at the College of New Jersey in Ewing who presented the research. Their definition is overly strict, he said, because they chose to model Earthlike planets without atmospheres or oceans. That’s simpler to simulate, but it also allows temperatures to fluctuate wildly on a planet as it orbits.
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“An atmosphere and oceans would smooth over temperature variations fairly well,” says study coauthor Mariah MacDonald, an astrobiologist also at the College of New Jersey. An abundance of air and water would potentially allow a planet to maintain habitable conditions, even if it spent more of its time outside of the nominal habitable zone around a binary star system.
The number of potentially habitable planets “will increase once we add atmospheres,” MacDonald says, “but I can’t yet say by how much.”
She and Pedowitz hope to build more sophisticated models in the coming months, as well as extend their simulations beyond a billion years and include changes in the stars that can affect conditions in a solar system as it ages.
The possibility of stable and habitable planets in binary star systems is a timely issue says Penn State astrophysicist Jason Wright, who was not involved in the study.
“At the time Star Wars came out,” he says, “we didn’t know of any planets outside the solar system, and wouldn’t for 15 years. Now we know that there are many and that they orbit these binary stars.”
These simulations of planets orbiting binaries could serve as a guide for future experiments, Wright says. “This is an under-explored population of planets. There’s no reason we can’t go after them, and studies like this are presumably showing us that it’s worthwhile to try.” More
