Two enormous Jupiter-like planets are orbiting a star about 400 light-years away – and one of them seems to be forming a moon. Researchers aimed the radio dishes of the Atacama Large Millimeter/submillimeter Array (ALMA) at the distant planetary system and captured a ring of material surrounding the planet.
That “disc” is exactly how astronomers think moons form. A planet’s gravity captures surrounding dust and gas, then its rotation whips that material into a spinning disc. Over time, the dust and gas falls together into moons. Astronomers still don’t fully understand how this process works, so they could learn a lot from studying this planet.
Similarly, the star itself has a disc – material that could one day coalesce into new planets.
“These new observations are also extremely important to prove theories of planet formation that could not be tested until now,” Jaehan Bae, a researcher at the Earth and Planets Laboratory of the Carnegie Institution for Science, who co-authored the study, said in a press release.
The first image, above, shows the star at the center of the disc. The system is called PDS 70, and the planet with the moon disc is called PDS 70c.
The planet’s moon-making halo, captured below, is about the width of the distance between Earth and the sun. That’s about 500 times larger than Saturn’s rings.
The disc contains enough material to make three moons the size of our own moon, according to the astronomers, who published their research in The Astrophysical Journal Letters on Thursday.
“In short, it is still unclear when, where, and how planets and moons form,” Stefano Facchini, a co-author of the study and research fellow at the European Southern Observatory, said in the release. “This system therefore offers us a unique opportunity to observe and study the processes of planet and satellite formation.”
The other planet circling this star does not show signs of a disc. The researchers said this could indicate that the moon-disc planet gobbled up all the available material, starving its twin. In addition to forming moons, the disc is likely helping the planet grow larger as material slowly falls into it.
The researchers plan to look at this star and its disc-adorned planet more closely with the Extremely Large Telescope, still under construction in Chile’s Atacama Desert. Once built, it will be the largest visible- and infrared-light telescope on Earth.
NASA is about to accomplish an unprecedented feat: The agency’s Perseverance Mars rover is set to film its own high-stakes landing.
The vehicle has almost reached its destination. On February 18, after nearly seven months and 300 million miles of space travel, the robot is slated to to plummet through the thin Martian atmosphere, deploy a parachute and a jetpack, then gently land in an ancient lake bed.
Once set up there, it will search for mineral deposits from an old lake, which could contain signs of ancient microbial life. The rover is programmed to cache samples of Martian rock and soil so that a future mission can carry them back to Earth for scientists to study.
But first, the rover must land successfully.
“I don’t think I’m exaggerating when I say that entry, descent, and landing is the most critical and most dangerous part of a mission,” Allen Chen, who leads that process for Perseverance at NASA’s Jet Propulsion Laboratory, said in a press briefing. “Success is never assured and that’s especially true when we’re trying to land the biggest, heaviest, and most complicated rover we’ve ever built to the most dangerous site we’ve ever attempted to land at.”
A series of precise, automated maneuvers must go exactly right to safely deliver Perseverance to its destination. There’s no room for error.
That’s why aerospace engineers have a special nickname for this phase of a Mars mission: “seven minutes of terror.”
For Perseverance, this process will be all the more terrifying because of its landing site. Mars’ Jezero Crater is a dried-up lake bed rich with exposed layers of ancient rock, which could hold remnants of past microbial life. Steep cliffs run through the middle of the landing site, along with sand dunes and boulders.
“Jezero Crater is a great place, magnificent place for science,” Chen said. “But when I look at it from a landing perspective, I see danger.”
If Perseverance arrives safely, however, it will then beam back the first video footage of a landing on another planet. High-definition cameras and microphones on the rover should record the whole thing, and NASA has said it will make the footage available later.
“We’re really looking forward to bringing everyone for the ride,” Chen said.
A parachute and a jetpack will slow Perseverance’s plummet
A NASA animation shows what the Perseverance landing should look like if all goes well:
The illustration below breaks down each step of that process.
“We’ve got literally seven minutes to get from the top of the atmosphere to the surface of Mars, going from 13,000 mph to zero in perfect sequence, perfect choreography, perfect timing,” Adam Steltzner, chief engineer of the Perseverance mission, said in a 2012 NASA-JPL video about the Curiosity rover (which is still going strong on Mars). “The computer has to do it all by itself with no help from the ground. If any one thing doesn’t work just right, it’s game over.”
The first step in Perseverance’s landing process is for the spacecraft that’s carried it 300 million miles to drop its cargo: a top-shaped capsule with the rover inside. This entry capsule will succumb to Mars’ gravity and plummet towards the planet, protecting Perseverance with a heat shield.
The capsule will plow through the Martian atmosphere at over 12,000 mph, and its shield should deflect material that’s been super-heated by that extreme speed. The outside of the heat shield will get as hot as 2,370 degrees Fahrenheit. This will cause it to streak across the Martian sky like a bright meteor.
Mars’ atmosphere is about 1% as thick as ours on Earth, but it should still slow the capsule down.
The capsule must use its thrusters to steer itself toward the landing target, since pockets of air with varying density can tilt it off-course.
Once it’s slowed to twice the speed of sound, Perseverance will deploy a 70-foot-wide parachute. Then the capsule will jettison its heat shield, clearing the way for the rover’s radar system to survey the land below. An autopilot-like navigation system should kick in to reconfigure the vehicle’s trajectory toward the landing site.
That system, called “terrain-relative navigation,” compares what the rover’s cameras see to an onboard map of the Martian surface, built from satellite imagery. It should recognize and avoid the cliffs, sand dunes, and boulder fields that litter Jezero Crater.
Perseverance’s supersonic parachute can only slow its descent to about 150 mph – as fast as a skydiver plummeting to Earth with no parachute. That’s why NASA engineers also equipped the rover with a jetpack.
About a mile above the Martian surface, the jetpack will ignite its engines, with the rover attached to its underside.
The jetpack will separate from the remaining parts of the entry capsule and fly Perseverance to a safe spot identified by the terrain-relative navigation. By the time the rover reaches its landing place, its speed should have slowed to about 1.5 mph.
Very slowly, the jetpack will unspool 25-foot-long nylon cords that will lower Perseverance until its wheels touch the ground.
A few minutes later, mission controllers should get the signal that the rover touched down.
After that, assuming everything has gone right, the rover will spend a few months checking and calibrating its scientific instruments. Then it will release a helicopter from its belly and turn its cameras to the drone as it lifts off for the first-ever controlled flight on another planet.
Then the rover will continue on its core mission: searching for ancient rocks that could hold hints of microbial alien life.
NASA sent its InSight lander to Mars with an ambitious mission: to study the planet’s deep internal structure. A crucial piece of that effort – the “mole” – has failed despite two years of attempts to salvage it.
The mole is a revolutionary heat probe designed to burrow 16 feet into the Martian soil and take the planet’s temperature. Its measurements would have revealed clues about how the planet formed and has changed over the last 4.6 billion years – a history that would help scientists track down Martian water, and possibly life.
But the mole has made little progress in the unexpectedly thick soil. Now the InSight team must ration the lander’s solar power. NASA announced Thursday that the mole won’t be able to dig its hole.
“It’s a bit of a personal tragedy,” Sue Smrekar, a lead scientist on the InSight team who has spent 10 years working on the mole, told Insider. “Everyone tried as hard as they could make it work. So I can’t ask for anything more than that.”
No other Mars mission in NASA’s foreseeable can take the internal temperature measurements for which the mole was designed.
“This has been our best attempt to get that data,” Smrekar added. “From my personal standpoint, it’s super disappointing, and scientifically it’s also a very significant loss. So it feels really like a huge letdown.”
An unexpected energy crisis
The InSight team spent two years maneuvering the lander’s robotic arm to see if it could help the mole burrow further. The probe, a 16-inch-long pile driver, is designed to leverage the loose dirt that other Mars missions have encountered. The soil would flow around the mole’s outer hull and provide friction to keep hammering deeper.
But in February 2019, the mole found itself bouncing in place on a foundation of firm soil called “duracrust.” The next two years were spent troubleshooting, beaming new software to InSight to teach its robotic arm new maneuvers to assist the mole, and anxiously waiting for photos that might show progress.
“It’s just been a huge effort across the board, and one that we never anticipated,” Smrekar said. “We thought that we were going to punch the hole down.”
The InSight team first instructed the robotic arm to push on the mole, but that just caused it to pop out of the hole. Once they got the probe back in the ground, a year later, they instructed the arm to pile dirt on top of it, hoping that would provide enough friction for the probe to dig deeper.
But the mole made no progress with 500 hammer strokes last Saturday. The top of it was just 2 or 3 centimeters below the surface.
By then, InSight’s problems were compounding. Unlike other sites where NASA has sent rovers and landers, the open plain where InSight sits wasn’t having powerful gusts of wind. Smrekar calls such gusts “cleaning events,” since they blow the planet’s pervasive red dust off any robots in the area. Without them, InSight’s solar panels have accumulated a significant layer of dust.
At the same time, the seasons were changing and InSight’s home on a flat plain near Mars’ equator was getting colder. In the chill, InSight will require more energy just to stay functional, even while its solar panels are absorbing less sunlight than they should.
“Power is decreasing and so we’re coming up on a time period where, for probably two or three months, we’re probably going to have to stand down from doing instrument operations for awhile and just kind of go into survival mode until it gets warmer on Mars,” Smrekar said.
With this new time constraint, Saturday’s hammering attempt was the mole’s last chance to burrow.
A planet’s internal temperature reveals its history
If the mole had hammered down to 16 feet below, it would have measured temperatures all the way down its hole. That would allow scientists to calculate how much heat is leaving Mars – a metric called “heat flow.”
“It’s a single number, the heat flow, but it has ramifications for all kinds of aspects of understanding Mars,” Smrekar said.
Heat leaving a planet is, in part, warmth left over from its formation, but it also comes from decaying radioactive elements. Measuring the heat flow would tell scientists how much radioactive material is inside the Martian crust – the outer layer of the planet – versus the mantle beneath.
That would reveal not only how material was distributed when the planet formed (and whether it’s made of the same stuff as Earth), but also how the planet’s internal structure has changed over time.
“That goes back to understanding the early evolution of Mars, that time period when there was a lot of liquid water on the surface,” Smrekar said.
A higher concentration of radioactive material in the mantle would make that layer more active. More radioactive material in the crust could keep the planet’s upper layers warm.
Heat flow could also indicate how deep you’d have to drill into Mars to reach liquid water today. Underground water on the planet could still host microbial life. Future humans traveling to Mars will likely need to harvest water there.
Now there is no possibility of measuring the planet’s heat flow in the foreseeable future.
“I was hoping to get the data and be able to understand what that means for Mars,” Smrekar said.