Space & Astronomy

Burning bits of ground-up meteorites may tell scientists what exoplanets’ early atmospheres are made of.
A set of experiments baking the pulverized space rocks suggests that rocky planets had early atmospheres full of water, astrophysicist Maggie Thompson of the University of California, Santa Cruz reported January 15 at the virtual meeting of the American Astronomical Society. The air could also have had carbon monoxide and carbon dioxide, with smaller amounts of hydrogen gas and hydrogen sulfide.
Astronomers have discovered thousands of planets orbiting other stars. Like the terrestrial planets in the solar system, many could have rocky surfaces beneath thin atmospheres. Existing and future space telescopes can peek at starlight filtering through those exoplanets’ atmospheres to figure out what chemicals they contain, and if any are hospitable to life (SN: 4/19/16).
Thompson and her colleagues are taking a different approach, working from the ground up. Instead of looking at the atmospheres themselves, she’s examining the rocky building blocks of planets to see what kind of atmospheres they can create (SN: 5/11/18).

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The researchers collected small samples, about three milligrams per experiment, of three different carbonaceous chondrite meteorites (SN: 8/27/20). These rocks are the first solids that condensed out of the disk of dust and gas that surrounded the young sun and ultimately formed the planets, scientists say. The meteorites form “a record of the original components that formed planetesimals and planets in our solar system,” Thompson said in a talk at the AAS meeting. Exoplanets probably formed from similar stuff.
The researchers ground the meteorites to powder, then heated the powder in a special furnace hooked up to a mass spectrometer that can detect trace amounts of different gases. As the powder warmed, the researchers could measure how much of each gas escaped.
That setup is analogous to how rocky planets formed their initial atmospheres after they solidified billions of years ago. Planets heated their original rocks with the decay of radioactive elements, collisions with asteroids or other planets, and with the leftover heat of their own formation. The warmed rocks let off gas. “Measuring the outgassing composition from meteorites can provide a range of atmospheric compositions for rocky exoplanets,” Thompson said.
All three meteorites mostly let off water vapor, which accounted for 62 percent of the gas emitted on average. The next most common gases were carbon monoxide and carbon dioxide, followed by hydrogen, hydrogen sulfide and some more complex gases that this early version of the experiment didn’t identify. Thompson says she hopes to identify those gases in future experimental runs.
The results indicate astronomers should expect water-rich steam atmospheres around young rocky exoplanets, at least as a first approximation. “In reality, the situation will be far more complicated,” Thompson said. Planets can be made of other kinds of rocks that would contribute other gases to their atmospheres, and geologic activity changes a planet’s atmosphere over time. After all, Earth’s breathable atmosphere is very different from Mars’ thin, carbon dioxide-rich air or Venus’s thick, hot, sulfurous soup (SN: 9/14/20).
Still, “this experimental framework takes an important step forward to connect rocky planet interiors and their early atmospheres,” she said.
This sort of basic research is useful because it “has put a quantitative compositional framework on what those planets might have looked like as they evolved,” says planetary scientist Kat Gardner-Vandy of Oklahoma State University in Stillwater, who was not involved in this new work. She studies meteorites too and is often asked whether experiments that crush the ancient, rare rocks are worth it.
“People inevitably will ask me, ‘Why would you take a piece of a meteorite and then ruin it?’” she says. “New knowledge from the study of meteorites is just as priceless as the meteorite itself.” More

An outburst from the super magnetic remains of a star suggests similar eruptions are behind some of the most powerful explosions in the universe. More

The most ancient black hole ever discovered is so big it defies explanation.
This active supermassive black hole, or quasar, boasts a mass of 1.6 billion suns and lies at the heart of a galaxy more than 13 billion light-years from Earth. The quasar, dubbed J0313-1806, dates back to when the universe was just 670 million years old, or about 5 percent of the universe’s current age. That makes J0313-1806 two times heavier and 20 million years older than the last record-holder for earliest known black hole (SN: 12/6/17).
Finding such a huge supermassive black hole so early in the universe’s history challenges astronomers’ understanding of how these cosmic beasts first formed, researchers reported January 12 at a virtual meeting of the American Astronomical Society and in a paper posted at arXiv.org on January 8.
Supermassive black holes are thought to grow from smaller seed black holes that gobble up matter. But astronomer Feige Wang of the University of Arizona and colleagues calculated that even if J0313-1806’s seed formed right after the first stars in the universe and grew as fast as possible, it would have needed a starting mass of at least 10,000 suns. The normal way seed black holes form — through the collapse of massive stars — can only make black holes up to a few thousand times as massive as the sun.
A gargantuan seed black hole may have formed through the direct collapse of vast amounts of primordial hydrogen gas, says study coauthor Xiaohui Fan, also an astronomer at the University of Arizona in Tucson. Or perhaps J0313-1806’s seed started out small, forming through stellar collapse, and black holes can grow a lot faster than scientists think. “Both possibilities exist, but neither is proven,” Fan says. “We have to look much earlier [in the universe] and look for much less massive black holes to see how these things grow.” More

The Parker Solar Probe is no stranger to the sun. On January 17, the NASA spacecraft will make its seventh close pass of our star, coming within 14 million kilometers of its scorching surface.
And this time, Parker will have plenty of company. A lucky celestial lineup means that dozens of other observatories will be trained on the sun at the same time. Together, these telescopes will provide unprecedented views of the sun, helping to solve some of the most enduring mysteries of our star.
“This next orbit is really an amazing one,” says mission project scientist Nour Raouafi of the Johns Hopkins Applied Physics Laboratory in Laurel, Md.
Chief among the spacecraft that will join the watch party is newcomer Solar Orbiter, which the European Space Agency launched in February 2020 (SN: 2/9/20). As Parker swings by our star this month, Solar Orbiter will be watching from the other side of the sun.

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“This is partially luck,” solar physicist Timothy Horbury of Imperial College London said  December 10 at a news briefing at the virtual meeting of the American Geophysical Union. “Nobody planned to have Parker Solar Probe and Solar Orbiter operating together; it’s just come out that way.”
Working together, the sungazers will tackle long-standing puzzles: how the sun creates and controls the solar wind, why solar activity changes over time and how to predict powerful solar outbursts.
“I think it genuinely is going to be a revolution,” Horbury said. “We’re all incredibly lucky to be doing this at this moment in time.”
Working in tandem
The Parker Solar Probe launched in 2018 and has already had six close encounters with the sun (SN: 7/5/18). During its nearly seven-year mission, the probe will eventually swing within 6 million kilometers of the sun — less than one-seventh the distance of Mercury from the sun — giving Parker’s heavily shielded instruments a better taste of the plasma and charged particles of the sun’s outer atmosphere, the corona (SN: 7/31/18).
Because Parker gets so close, its cameras cannot take direct pictures of the solar surface. Solar Orbiter, though, will get no closer than 42 million kilometers, letting it take the highest-resolution images of the sun ever. The mission’s official science phase won’t begin until November 2021, but the spacecraft has already snapped images revealing tiny “campfire” flares that might help heat the corona (SN: 7/16/20).
During Parker’s seventh close encounter, which runs January 12–23, Solar Orbiter will observe the sun from a vantage point almost opposite to Parker’s view. Half a dozen other observers will be watching as well, such as ESA’s BepiColombo spacecraft that is on its way to Mercury and NASA’s veteran sunwatcher STEREO-A. Both will flank Parker on either side of the sun. And telescopes on Earth will be watching from a vantage point about 135 million kilometers behind Parker, making a straight line from Earth to the spacecraft to the sun.
When the Parker Solar Probe makes its next close pass of the sun (shown in the black arc in the center of this diagram), a host of other spacecraft and telescopes on Earth will be watching too. This diagram shows the relative positions during the flyby of the sun, Earth, Parker, Solar Orbiter and two other spacecraft, BepiColombo and STEREO-A.JHU-APL
When the Parker Solar Probe makes its next close pass of the sun (shown in the black arc in the center of this diagram), a host of other spacecraft and telescopes on Earth will be watching too. This diagram shows the relative positions during the flyby of the sun, Earth, Parker, Solar Orbiter and two other spacecraft, BepiColombo and STEREO-A.JHU-APL
The situation is similar to Parker’s fourth flyby in January 2020, when nearly 50 observatories watched the sun in tandem with the probe, Raouafi says. Those observations led to a special issue of Astronomy & Astrophysics with more than 40 articles. One of the results was confirming that there is a region around the sun that is free of dust, which was predicted in 1929. “That was amazing,” Raouafi says. “We want to do a campaign that is that good or even better for this run.”
In the wind
At the AGU meeting, researchers presented new results from Parker’s second year of observations. The results deepen the mystery of magnetic kinks called “switchbacks” that Parker observed in the solar wind, a constant stream of charged particles flowing away from the sun (SN: 12/4/19), Raouafi says.
Some observations support the idea that the kinks originate at the base of the corona and are carried past Parker and beyond, like a wave traveling along a jump rope. Others suggest the switchbacks are created by turbulence within the solar wind itself.
Figuring out which idea is correct could help pinpoint how the sun produces the solar wind in the first place. “These [switchbacks] could be the key to explaining how the solar wind is heated and accelerated,” Raouafi said in a talk recorded for AGU.
Meanwhile, Solar Orbiter’s zoomed-in images plus simultaneous measurements of the solar wind may allow scientists to trace the wind’s energetic particles back to their birthplaces on the sun’s surface. Campfire flares — the “nanoflares” spotted by Solar Orbiter — might even explain the switchbacks, Horbury says.
“The goal is to connect tiny transient events like nanoflares to changes in the solar wind,” Horbury said in the news briefing.
Waking up with the sun
Parker and Solar Orbiter couldn’t have arrived at a better time. “The sun has been very quiet, in a deep solar minimum for the last several years,” Horbury said. “But the sun is just beginning to wake up now.”
Both spacecraft have seen solar activity building over the last year. During its sleepy period, the sun displays fewer sunspots and outbursts such as flares and coronal mass ejections, or CMEs. But as it wakes up, those signs of increasing magnetic activity become more common and more energetic.
On November 29, Parker observed the most powerful flare it had seen in the last three years, followed by a CME that ripped past the spacecraft at 1,400 kilometers per second.“We got so much data from that,” Raouafi says. More CMEs should pass Parker when it’s even closer to the sun, which will tell scientists about how these outbursts are launched.
Solar Orbiter caught an outburst too. On April 19, a CME passed the spacecraft about 20 hours before its effects arrived at Earth. With existing spacecraft, observers on Earth get only about 40 minutes warning before a CME arrives.
Solar Orbiter detected a big burst of plasma called a coronal mass ejection in April, almost a day before signs of the eruption reached Earth. Observers on Earth typically get just 40 minutes of warning before such an eruption arrives.ESA
Solar Orbiter detected a big burst of plasma called a coronal mass ejection in April, almost a day before signs of the eruption reached Earth. Observers on Earth typically get just 40 minutes of warning before such an eruption arrives.ESA
“We can see how that CME evolves as it travels away from the sun in a way we’ve never been able to do before,” Horbury said.
Strong CMEs can knock out satellites and power grids, so having as much forewarning as possible is important. A future spacecraft at Solar Orbiter’s distance from the sun could help give that warning.
Looking forward
This orbit is the first time that Parker Solar Probe and Solar Orbiter will watch the sun in tandem, but not the last. “There will be plenty of opportunities like this one,” Raouafi says.
He’s looking forward to one opportunity in particular: the solar eclipse of 2024. On April 8, 2024, a total eclipse will cross North America from Mexico to Newfoundland. Solar scientists plan to make observations from all along the path of totality, similar to how they watched the total eclipse of 2017.
During the eclipse, the Parker Solar Probe will be on its second-closest orbit, between 7 million and 8 million kilometers from the sun. Parker and Solar Orbiter will be “almost on top of each other,” Raouafi says — both spacecraft will be together off to one side of the sun as seen from Earth. Whatever prominences and other shapes in the corona are visible to observers on Earth will be headed right at the spacecraft.
“They will be flying through the structure we will see from Earth during the solar eclipse,” Raouafi says. The combined observations will tell scientists how features on the sun evolve with time.
“I think it is a new era,” Horbury said. “The next few years is going to be a step change in the way we see the sun.” More

The best way to know a world is to touch it. Scientists have observed the planets and moons in our solar system for centuries, and have flown spacecraft past the orbs for decades. But to really understand these worlds, researchers need to get their hands dirty — or at least a spacecraft’s landing pads.
Since the dawn of the space age, Mars and the moon have gotten almost all the lander love. Only a handful of spacecraft have landed on Venus, our other nearest neighbor world, and none have touched down on Europa, an icy moon of Jupiter thought to be one of the best places in the solar system to look for present-day life (SN: 5/2/14).
Researchers are working to change that. In several talks at the virtual American Geophysical Union meeting that ran from December 1 to December 17, planetary scientists and engineers discussed new tricks that hypothetical future spacecraft may need to land on unfamiliar terrain on Venus and Europa. The missions are still in a design phase and are not on NASA’s launch schedule, but scientists want to be prepared.

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Navigating a Venusian gauntlet
Venus is a notoriously difficult world to visit (SN: 2/13/18). Its searing temperatures and crushing atmospheric pressure have destroyed every spacecraft lucky enough to reach the surface within about two hours of arrival. The last landing was over 30 years ago, despite increasing confidence among planetary scientists that Venus’ surface was once habitable (SN: 8/26/16). That possibility of past, and perhaps current, life on Venus is one reason scientists are anxious to get back (SN: 10/28/20).
In one of the proposed plans discussed at the AGU meeting, scientists have ridged, folded mountainous terrain on Venus called tessera in their sights. “Safely landing in tessera terrain is absolutely necessary to satisfy our science objectives,” said planetary scientist Joshua Knicely of the University of Alaska Fairbanks in a talk recorded for the meeting. “We have to do it.”
Knicely is part of a study led by geologist Martha Gilmore of Wesleyan University in Middletown, Conn., to design a hypothetical mission to Venus that could launch in the 2030s. The mission would include three orbiters, an aerobot to float in the clouds and a lander that could drill and analyze samples of tessera rocks. This terrain is thought to have formed where edges of continents slid over and under each other long ago, bringing new rock up to the surface in what might have been some version of plate tectonics. On Earth, this sort of resurfacing may have been important in making the planet hospitable to life (SN: 4/22/20).
Ridged, folded mountainous terrain on Venus called tessera (bright region in this false-color image from NASA’s Magellan spacecraft) might have formed through long-ago tectonic activity.JPL-Caltech/NASA
But landing in these areas on Venus could be especially difficult. Unfortunately, the best maps of the planet — from NASA’s Magellan orbiter in the 1990s — can’t tell engineers how steep the slopes are in tessera terrain. Those maps suggest that most are less than 30 degrees, which the lander could handle with four telescoping legs. But some could be up to 60 degrees, leaving the spacecraft vulnerable to toppling over.
“We have a very poor understanding of what the surface is like,” Gilmore said in a talk recorded for the meeting. “What’s the boulder size? What’s the rock size distribution? Is it fluffy?”
So the lander will need some kind of intelligent navigation system to pick out the best places to land and steer there. But that need for steering brings up another problem: Unlike landers on Mars, a Venus lander can’t use small rocket engines to slow down as it descends.
The shape of a rocket is tailored to the density of air that it will push against. That’s why rockets that launch spacecraft from Earth have two sections: one for Earth’s atmosphere and one for the near-vacuum of space. Venus’ atmosphere changes density and pressure so quickly between space and the planet’s surface that “dropping a kilometer would go from the rocket working perfectly, to it’s going to misfire and possibly blow itself apart,” Knicely says.
Instead of rockets, the proposed lander would use fans to push itself around, almost like a submarine, turning the disadvantage of the dense atmosphere into an advantage.
The planet’s atmosphere also presents the biggest challenge of all: seeing the ground. Venus’ dense atmosphere scatters light more than Earth’s or Mars’ does, blurring the view of the surface until the last few kilometers of descent.
Worse, the scattered light makes it seem like illumination is coming from all directions at once, like shining a flashlight into fog. There are no shadows to help show steep slopes or reveal big boulders that the lander could crash into. That’s a major issue, according to Knicely, because all of the existing navigation software assumes that light comes from just one direction.
“If we can’t see the ground, we can’t find out where the safe stuff is,” Knicely says. “And we also can’t find out where the science is.” While proposed solutions to the other challenges of landing on Venus are close to doable, he says, this one remains the biggest hurdle.
Sticking the landing on Europa
Jupiter’s icy moon Europa, on the other hand, has no air to blur the surface or break rockets. A hypothetical future Europa lander, also discussed at the AGU meeting, would be able to use the “sky crane” technique (SN: 8/6/12). That method, in which a platform hovers above the surface using rockets and drops a spacecraft to the ground, was used to land the Curiosity rover on Mars in 2012 and will be used for the Perseverance lander in February 2021.
“The engineers are very excited about not having to deal with an atmosphere on the way down,” said spacecraft engineer Jo Pitesky of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., in a recorded talk for the meeting.
Still, there’s a lot that scientists don’t know about Europa’s surface, which could have implications for any lander that touches down, said planetary scientist Marissa Cameron of the Jet Propulsion Laboratory in another talk.
The best views of the moon’s landscape are from the Galileo orbiter in the 1990s, and the smallest features it could see were half a kilometer across. Some scientists have suggested that Europa could sport jagged ice spikes called penitentes, similar to ice features in the Chilean Andes Mountains that are named for their resemblance to hooded monks with bowed heads — although more recent work shows Europa’s lack of atmosphere should keep penitentes from forming.
Another mission, the Europa Clipper, that’s already underway will take higher-resolution images when the orbiter visits the Jovian moon later this decade, which should help clarify the issue.
In the meantime, scientists and engineers are running elaborate dress rehearsals for a Europa landing, from simulating ices with different chemical compositions in vacuum chambers to dropping a dummy lander named Olaf from a crane to see how it holds up.
“We have a requirement that says the terrain can have any configuration — jagged, potholes, you name it — and we have to be able to conform to that surface and be stable at it,” says John Gallon, an engineer at the Jet Propulsion Laboratory. (The dummy lander was named for his 4-year-old daughter’s favorite character in the movie Frozen.)
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Olaf, a scale model of a possible Europa lander, is helping NASA engineers test different strategies for landing on the icy moon of Jupiter. The rover is named for the snowman in the movie Frozen.
Over the last two years, Gallon and colleagues have tested different lander feet, legs and configurations in a lab by suspending the lander from the ceiling like a marionette. That suspension helps simulate Europa’s gravity, which is one-seventh that of Earth’s.
Without much gravity, a massive lander could easily bounce around and damage itself when trying to land. “You’re not going to stick the landing like a gymnast coming off the bars,” Gallon says. His team has tried sticky feet, bowl-shaped feet, springs that compress and push into the surface and legs that lock to help the lander stay put on various terrains. The lander might crouch like a frog or stand stiff like a table, depending on what type of surface it lands on.
Although Olaf is hard at work helping scientists figure out what it will take to build a successful Europa lander, the mission itself, like its Venusian counterpart, remains only on some planetary scientists’ wish lists for now. Meanwhile, other researchers dream about voyages to entirely different worlds, including Saturn’s geyser moon Enceladus.
“Some people will pick favorites,” Cameron says. “I just want to land someplace we’ve never been to that’s not Mars. I’d love that.” More