Ingenuity is still flying on Mars. Here’s what the helicopter is up to

The Ingenuity Mars helicopter was never supposed to last this long. NASA engineers built and tested the first self-powered aircraft to fly on another planet to answer a simple question: Could the helicopter fly at all? The goal was to take five flights in 30 Martian days or break the aircraft trying.

But more than 120 Martian days past that experiment window, Ingenuity is still flying and doing things no one ever expected. The helicopter, which took its first flight on April 19, is breaking its own records for distance and speed (SN: 4/19/21). It’s helping the Perseverance rover explore Jezero crater, near an ancient river delta that may hold signs of past Martian life (SN: 2/17/21). And Ingenuity is coping with changing seasons and navigating over rough terrain, two things that the flier wasn’t designed to do.

“It’s gotten into a good groove,” says Ingenuity’s original chief engineer Bob Balaram NASA’s Jet Propulsion Lab in Pasadena, Calif. “It’s in its element and having fun.”

Here’s what Ingenuity has been up to on Mars.
Testing the limits
Ingenuity is flying farther, faster and higher than it did in its first few flights. The helicopter has lifted itself a maximum of 12 meters above the Martian surface, zipped along at up to five meters per second (about half as fast as record-setting sprinter Florence Griffith-Joyner) and covered 625 meters (about a third the length of the Kentucky Derby) in a single flight. These extremes give engineers valuable information about the limits of flying on Mars.

“We are still trying to learn lessons,” says JPL robotics engineer Teddy Tzanetos, a team leader for the Ingenuity mission. “Flight after flight, we’re learning the boundaries of performance.”
Early on, Ingenuity tested its limits in a way that the flight team really didn’t plan for. During its sixth flight on May 22, the helicopter’s navigation system suffered a glitch that made it roll and sway alarmingly.

The helicopter’s navigation software keeps track of the craft’s position by taking an image, reading the time stamp on that image and predicting what the camera should see next based on landmarks from previous photos that Ingenuity took. If the next image doesn’t match that prediction, the software corrects the helicopter’s position and velocity to match up better.

Less than a minute into the May 22 flight, a single image got lost on its way from Ingenuity’s cameras to its onboard computer. That meant that the time stamps on all subsequent images were a little off. In trying to correct what it perceived as errors, Ingenuity “went on a wild joyride,” Balaram says.

Luckily, the helicopter touched down safely within five meters of its intended landing spot. The anomaly was a blessing in disguise, Balaram says. It put the helicopter through extremes of movement — “how aggressively you can move the joystick, if you will” — that the engineers would not have asked it to do on purpose, and did perfectly fine, he says.

“It’s a serendipitous thing that we got that flight experience under our belt,” Balaram says. “We have much more confidence in the vehicle.”

Doing science
Originally, the helicopter team wanted to push the vehicle until it broke. But now the researchers are flying more cautiously and less often. That’s because the helicopter is currently supporting the Perseverance rover in doing science (SN: 4/30/21).

“We’re no longer in the Month of Ingenuity,” Tzanetos says. “We’re a small part of a much larger team.”

The helicopter has already proven its worth by telling the rover where not to go. Ingenuity’s ninth flight, on July 5, took the helicopter over a dune field called South Séítah that would have been difficult for the rover to drive through safely. Then, Ingenuity photographed some rock outcrops and raised ridges in South Séítah that had looked interesting in images taken from an orbiting spacecraft. Scientists thought those ridges could record some of the deepest water environments in the lake that filled the crater long ago.
In 3-D images from the helicopter, it turned out that those ridges did not show the layers that would have indicated that the rocks formed in deep water. The rover team decided to move on, saving Perseverance a long, arduous and potentially dangerous drive.

“They didn’t have to send the rover all the way to this particular target, and then realize, hey, this may not be the highest priority thing,” Balaram says.

Scouting for the rover has also taken Ingenuity over terrain that the helicopter wasn’t designed to understand. Ingenuity’s navigation software was programmed to assume that the ground beneath it is always flat because that was the type of terrain selected for that experimental first month of flight demonstrations.

“It was a perfectly reasonable simplification for a technology demonstration,” Balaram says. “But it was baked in. And now you’re stuck with a system with a flat ground assumption.”

When the helicopter is flying over a sloped surface, some features seem to move faster in its view than they would if the ground were flat, giving the helicopter a false sense of its motion. “The onboard navigation has no way of explaining it, except for thinking maybe I’m turning or spinning a bit,” Balaram says. The helicopter ends up veering to the side.

The team has come up with some work-arounds, such as choosing large enough landing zones that a precision landing isn’t necessary and slowing down when flying over rough terrain.

Coping with seasons
The air on Mars is notoriously thin (SN: 7/14/20). But since mid-September, the atmosphere in Jezero crater has been getting even thinner. As that part of Mars shifts from spring to summer, the air density has gone from about 1.5 percent of Earth’s at sea level, to about 1 percent.

That doesn’t sound like a big difference, but it’s enough that Ingenuity has had to spin its rotor blades faster to stay aloft. In October, the helicopter increased its rotor speed to 2,700 revolutions per minute, compared with a previous maximum of 2,537 rpm.
At that faster spin speed, the helicopter can fly for only 130 seconds at a time instead of the 170 seconds it managed before, without running the risk of the motors overheating.

That would be fine if the helicopter was just going to hang around the rover in one area, Tzanetos says. But the Mars duo’s next task is a race to the long-dry river delta at the mouth of Jezero crater. The Perseverance team hopes to cover hundreds of meters each Martian day. The farthest Ingenuity has covered in a day is 625 meters, and that was with the lower spin speed.

“It’ll be challenging to keep up,” Tzanetos says.

There’s no technical reason why Ingenuity can’t make it, though, Balaram says. “It’s certainly possible that one day it just won’t wake up. Or a landing will be a failure and we’ll never hear from it again because it tipped over,” he admits. “Those are rolls of the dice, there’s nothing inevitable about those. Barring that, it should keep working for many months.”

Inspiring future fliers
Meanwhile, engineers are already dreaming of the next Martian aircraft.

“Ingenuity is very exciting, we’re breaking a lot of ground,” Tzanetos says. “The whole point of it is to be that foundation. The important thing is what comes next.”

Current blueprints include a scaled-up version of Ingenuity that could carry more equipment and work alone or with a rover, and a large hexacopter, with six rotors arranged around a central ring. A craft like that could cover more ground more quickly than a rover, traveling distances that could take Perseverance multiple years in just a few months.

A white paper submitted to the 2023–2032 planetary science and astrobiology decadal survey — a once-a-decade review of the fields’ goals and priorities — suggests several possible missions for a Mars Science Helicopter. In one, the craft could take samples of clay minerals at a site like Mawrth Vallis, a channel thought to be carved by a long-ago flood.
Mawrth was a finalist for the last two Mars rover landing sites and is a contender for the European Space Agency’s Rosalind Franklin rover, set to launch in 2022. Clays can preserve organic material on Earth, so a mission to Mawrth could search for signs of life.

A helicopter could also explore craters with water ice deposits with slopes too steep for rover wheels. And by taking measurements at several different altitudes, the helicopter could help figure out how the atmosphere exchanges gases with the ground, which could help solve the mystery of when and how Mars lost its liquid water (SN: 11/12/20). Or a helicopter could map the magnetic field of large swaths of the Martian surface, revealing when and how the Red Planet lost its molten core (SN: 2/24/20).

And whenever astronauts get around to visiting Mars, “it might be useful to have fleets of drones zipping around the skies, carrying loads or scouting ahead,” Tzanetos says. “That’s the exciting future I’m looking forward to.”

50 years ago, chemical pollutants were linked to odd animal behavior

For fish and other underwater life, a sensitivity to chemicals plays the same role as the sense of smell does for land animals.… [Researchers] have been studying the subtle ways this delicate fish-communication system can be disrupted by pollutants…. One study examined the effects of kerosene pollution on the behavior of lobsters…. The experiments demonstrate that chemical communication interference takes place at extremely low dilutions.

Update
Chemical pollution — from sewage and agricultural runoff to pharmaceutical waste — muddles aquatic animals’ senses with potentially dire effects, decades of research has shown. A chemical used to treat sewage seems to limit some fish species’ abilities to form schools, making the fish vulnerable to predators (SN: 10/27/07, p. 262). Drug-tainted waters can have a variety of effects on fish, including suppressing their appetites (SN: 12/20/08, p. 15). A plastic chemical also appears to confuse senses: Its scent can lure sea turtles into eating plastic debris (SN: 3/28/20, p. 14).

Ripples in rats’ brains tied to memory may also reduce sugar levels

Ripples of nerve cell activity that lock in memories may have an unexpected job outside of the brain: Dropping blood sugar levels in the body.

Just after a burst of ripples in a rat’s hippocampus, sugar levels elsewhere in the body dipped, new experiments show. The curveball results, published August 11 in Nature, suggest that certain types of brain activity and metabolism are entwined in surprising and mysterious ways.

“This paper represents a significant advance in our understanding of how the hippocampus modulates metabolism,” says Elizabeth Gould, a neuroscientist at Princeton University who wasn’t involved in the study.

Neural shudders called sharp-wave ripples zig and zag in the brains of people as they learn new things and draw memories back up (SN: 8/19/19). Ripples also feature prominently during deep sleep. Sleeping mammals, birds and even lizards known as Australian dragons have these bursts of electrical activity. Sharp-wave ripples are thought to accompany the neural work of transforming short-term knowledge into long-term memories.
Neuroscientist David Tingley wondered whether these signals might also change something outside of the brain. Working with neuroscientist György Buzsáki at New York University Grossman School of Medicine and colleagues, Tingley, now at Harvard University, fitted continuous glucose monitors onto the backs of rats. These devices, used by people with diabetes to keep tabs on sugar levels in the fluid around cells, provide a good proxy for blood sugar levels. The researchers simultaneously measured the rats’ brain waves with electrodes implanted in the hippocampus, a brain structure that plays a key role in memory.

Every so often, electrodes picked up clusters of ripples. About 10 minutes after a bout of ripples, sugar levels in the body fell, the glucose monitors showed. “We saw these dips in the second rat, and the third rat, and the fourth rat,” says Buzsáki. “It was super consistent. The magnitude is small but [the dips] are always there.”

To see if this connection between the ripples and the sugar dips was mere coincidence, the researchers forced nerve cells in the hippocampus to fire in response to light, creating artificial ripples. Sure enough, after a bout of these forced ripples, the rats’ sugar levels dropped.

What’s more, when the researchers jammed the ripples’ downstream signals with a drug that quiets nerve cells in a brain area called the lateral septum, sugar levels did not drop. That suggests these ripples send signals that ping-pong through the brain and ultimately tell the body to reduce its sugar.

“All of this was very surprising,” says Jan Born, a neuroscientist who studies metabolism at the University of Tübingen in Germany. You might expect a busy brain at work to call for more energy, in the form of sugar, not less, says Born, who cowrote a commentary on the new paper in the same issue of Nature. But here, “the brain says to the body, ‘We don’t need so much energy, so go down with your glucose levels.’ Why?” says Born, “It’s difficult to see its function.”

Buzsáki wonders whether these ripples might have evolved initially to aid in metabolism. “They were useful for the body first,” he speculates. As time passed, ripples may have been pulled in on other jobs, such as memory storage.

If this newfound link between brain waves and metabolism exists in people, it might suggest a way to influence sugar levels by tweaking ripples, Buzsáki says, an idea that might prove useful for people with diabetes or other metabolic problems. The hippocampus is deep in the brain, but its activity can be altered via magnetic or electrical jolts to easier-to-reach brain areas. Still, changing ripples for metabolic reasons is a far-off idea, Buzsáki cautions.

A clever genetic tool tackles new troubles

Stanley Qi
Bioengineer
Stanford University

By disabling the DNA-cutting enzyme in the CRISPR system, Stanley Qi, featured in 2019, created a new and versatile tool. Attaching a range of molecules to these “dead Cas” enzymes has yielded an entire toolbox worth of DNA and RNA manipulators.

Is the strategy of disabling Cas molecules still popular among researchers?
I feel it’s getting more popular, for a number of reasons: One, people use … this tool to study how the genome works. Two, there are some new efforts using the tool to treat some genetic diseases. And three, there are some other exciting uses of this tool to think about other diseases, other topics that we can possibly tackle.

For example, this CRISPR system came from bacteria cells, right? They were used as weapons by the bacteria to fight against invading viruses. So we said, “OK, humans also have many foes like invading viruses. Can we repurpose this CRISPR to help us fight our infectious diseases?” That was the idea before the COVID-19 pandemic. We practiced first on influenza, seasonal flu…. We adapted a type of CRISPR system that targets a specific RNA molecule, and it works pretty well. I remember it working in January [2020] when the news started reporting, “Oh, there’s a new virus, it’s an RNA virus,” and we thought immediately, “What if we use this tool on this new RNA virus?”

Instead [of using the live virus], we used synthetic biology to mimic the RNA sequence.… [And we found] we can still very rapidly cleave and destroy this RNA virus and its fragments in the human lung cells. We were really excited. Since then we’ve been working very hard to follow up on the idea, to make this as fast as possible into a possible antiviral. We called it PAC-MAN.

Can you talk a bit about how the dead Cas, or dCas, approach has been improved and adapted?
One bigger use is for treating disease like a gene therapy. However, there’s still a number of features that have not been ideal for easy use or testing in clinics.… [For patient care,] people always think about making the system very, very compact and suitable into a nanoparticle or into a viral particle, so we can deliver them with ease into the human body. So that requires a miniaturization of the CRISPR system. And we actually did some work on that…. They are like two-thirds smaller than what people use.

And second is, many of these natural proteins from bacteria don’t work very well [in human cells].… So we did some protein engineering. Following these efforts, we actually created some highly compact, yet highly efficient dCas systems that can be easily delivered into the human body to turn on or off genes.

What are the greatest challenges you’ve faced in the last couple of years?
We are bioengineers and we think our strength is in creating stuff, modifying. Now as we step into the domain of applying these tools to solve real-world problems, the challenge is how to build a bridge between where we are to where we want to go. That usually requires learning a significant amount about a disease, about a new field, and thinking creatively on how to interface two fields.

— Interview by Ashley Braun

Pluto’s dark side reveals clues to its atmosphere and frost cycles

Pluto’s dark side has come into dim view, thanks to the light of the dwarf planet’s moon.

When NASA’s New Horizons spacecraft flew past Pluto in 2015, almost all the images of the dwarf planet’s unexpectedly complex surface were of the side illuminated by the sun (SN: 7/15/15). Darkness shrouded the dwarf planet’s other hemisphere. Some of it, like the area near the south pole, hadn’t seen the sun for decades.

Now, mission scientists have finally released a grainy view of the dwarf planet’s dark side. The researchers describe the process to take the photo and what it tells them about how Pluto’s nitrogen cycle affects its atmosphere October 20 in the Planetary Science Journal.

Before New Horizons passed by Pluto, the team suspected the dwarf planet’s largest moon, Charon, might reflect enough light to illuminate the distant world’s surface. So the researchers had the spacecraft turn back toward the sun to take a parting peek at Pluto.
At first, the images just showed a ring of sunlight filtering through Pluto’s hazy atmosphere (SN: 7/24/15). “It’s very hard to see anything in that glare,” says planetary scientist John Spencer of the Southwest Research Institute in Boulder, Colo. “It’s like trying to read a street sign when you’re driving toward the setting sun and you have a dirty windshield.”

Spencer and colleagues took a few steps to make it possible to pull details of Pluto’s dark side out of the glare. First, the team had the spacecraft take 360 short snapshots of the backlit dwarf planet. Each was about 0.4 seconds long, to avoid overexposing the images. The team also took snapshots of the sun without Pluto in the frame so that the sun could be subtracted out after the fact.

Tod Lauer of the National Optical Astronomy Observatory in Tucson, Ariz., tried to process the images when he got the data in 2016. At the time, the rest of the data from New Horizons was still fresh and took up most of his attention, so he didn’t have the time to tackle such a tricky project.

But “it was something that just sat there and ate away at me,” Lauer says. He tried again in 2019. Because the spacecraft was moving as it took the images, each image was a little bit smeared or blurred. Lauer wrote a computer code to remove that blur from each individual frame. Then he added the reflected Charon light in each of those hundreds of images together to produce a single image.
“When Tod did that painstaking analysis, we finally saw something emerging in the dark there … giving us a little bit of a glimpse of what the dark pole of Pluto looks like,” Spencer says.

That the team got anything at all is impressive, says planetary scientist Carly Howett, also of the Southwest Research Institute and who is on the New Horizons team but was not involved in this work. “This dataset is really, really hard to work with,” she says. “Kudos to this team. I wouldn’t have wanted to do this.”

The image, Howett says, can help scientists understand how Pluto’s frigid nitrogen atmosphere varies with its decades-long seasons. Pluto’s atmosphere is controlled by how much nitrogen is in a gas phase in the air and how much is frozen on the surface. The more nitrogen ice that evaporates, the thicker the atmosphere becomes. If too much nitrogen freezes to the ground, the atmosphere could collapse altogether.
When New Horizons was there, Pluto’s south pole looked darker than the north pole. That suggests there was not a lot of fresh nitrogen frost freezing out of the atmosphere there, even though it was nearing winter. “The previous summer ended decades ago, but Pluto cools off pretty slowly,” Spencer says. “Maybe it’s still so warm [that] the frost can’t condense there, and that keeps the atmosphere from collapsing.”

There was a bright spot in the middle of the image, which could be a fresh ice deposit. That’s also not surprising, Howett says. The ices may still be moving from the north pole to the south pole as Pluto moves deeper into its wintertime.

“We’ve thought this for a long time. It makes sense,” she says. “But it’s nice to see it happening.”

An easier, greener way to build molecules wins the chemistry Nobel Prize

Making molecules is hard work. Atoms must be stitched together into specific arrangements through a series of chemical reactions that are often slow, convoluted and wasteful. The 2021 Nobel Prize in chemistry recognizes two scientists who developed a tool at the turn of the century that revolutionized how chemists construct new molecules, making the process faster and more environmentally friendly.

Chemists Benjamin List of the Max-Planck-Institut für Kohlenforschung in Mülheim an der Ruhr, Germany and David MacMillan of Princeton University were awarded the prize for independently developing organic catalysts that speed up chemical reactions necessary for constructing specific molecules, a process called asymmetric organocatalysis. The two will share the prize of 10 million Swedish kroner (more than $1.1 million), the Royal Swedish Academy of Sciences announced October 6 in a news conference in Stockholm.

“This is a fitting recognition of very important work,” says H.N. Cheng, president of the American Chemical Society.

“We can think of chemists as magicians having magic wands in the lab,” Cheng says. “We wave the wand and a reaction goes on.” These Nobel laureates gave chemists “a new wand,” that’s drastically more efficient and less wasteful, he says.

Making new drugs or designing novel materials often requires building new molecules from simpler chemical building blocks. But these chemical building blocks can’t just be thrown together. Instead, they must be carefully combined in precise arrangements through a series of chemical reactions. Many chemical reactions produce two versions of a molecule that are mirror images of one another, and often those two versions can have very different effects. For example, thalidomide, a drug prescribed in the 1950s and ‘60s for morning sickness, caused birth defects in more than 10,000 babies because of one mirror image of this molecule (SN: 12/24/94). Consequently, building these asymmetric molecules and controlling which version of a molecule gets produced is extremely important, especially for drug development.
Chemical reactions can be coaxed along by catalysts — molecular workhorses that accelerate chemical reactions without being transformed by them. Historically, chemists have known about two kinds of catalysts: enzymes and metal complexes. Enzymes are big, clunky proteins that have been honed by evolution to perform very specific chemical actions in the body, but they can be difficult to use on a large scale in the lab. Metals, such as platinum or cobalt, can kick-start some reactions too, but many only work in airless, waterless environments that are difficult to achieve in manufacturing contexts (SN: 2/21/17). Additionally, many metal catalysts are also toxic to the environment and expensive to procure.

For much of the history of chemistry, these were the only tools available to chemists who wanted to make new molecules. “But in the year 2000, everything changed,” Pernilla Wittung-Stafshede, a chemist at Chalmers University of Technology in Gothenburg, Sweden and a member of the Nobel Committee for Chemistry, said during the news conference.

Benjamin List, then at Scripps Research Institute in La Jolla, Calif., was studying the aldol reaction, which links two molecules together through carbon bonds. In organisms, such reactions are crucial for converting food into energy, and depend on a large and complex enzyme called aldolase A. Only a small part of the enzyme actually catalyzes the reaction, however, and List discovered that a single amino acid — proline — could do the work of this big clunky protein while also producing one version of the final product much more often than the other.
“When I did this experiment, I didn’t know what would happen and I thought maybe it’s a stupid idea,” List said during the news conference. “When I saw it work, I did feel it could be something big.”

Unbeknown to List, MacMillan was also looking for alternative organic catalysts around the same time. MacMillan, then at the University of California, Berkeley, focused on another chemical reaction, the Diels-Alder reaction, which forms rings of carbon atoms (SN: 11/18/50). It’s an important reaction, used today to make products as different as rubber and pharmaceuticals, but was very slow and relied on finicky metal catalysts that wouldn’t work when wet. MacMillan designed small organic molecules that mimicked the catalytic action of metals in a simpler way, while also favoring the production of one of two possible mirror images of the final product. He coined this new kind of catalysis “asymmetric organocatalysis.”

List’s and MacMillan’s discoveries set off an explosion of research into finding more organocatalysts over the next two decades, work that’s aided drug discovery among other uses.

About 35 percent of the world’s gross domestic product depends on catalysis, Peter Somfai, a chemist at Lund University in Sweden and a member of the Nobel Committee for Chemistry, said during the news conference. “We now have a new powerful tool available for making organic molecules,” one that can be drastically more efficient and greener than previous methods.

Somfai highlighted this leap forward in efficiency using the neurotoxin strychnine. The molecule itself isn’t useful for chemists, but its complicated structure makes it a good benchmark for comparing different synthesis methodologies. Previously, chemists relied on an extremely wasteful process of 29 different reactions where just 0.0009 percent of the initial material became strychnine. Using organocatalysis, strychnine can now be synthesized in just 12 steps, and the whole process is 7,000 times more efficient, Somfai said. And because this extra efficiency is gained without using toxic metals, organocatalysis is a more environmentally friendly way of synthesizing chemicals.

If building new molecules is like playing chess, organocatalysis has “completely changed the game,” Somfai said. “It’s like adding a new chess piece that can move in different ways.”