The Aging Spacecraft of Deep Space

Uranus as seen by Voyager 2 on its way deeper into space

Beyond Earth and its bubble of satellites; past Mars, where rovers explore; past Jupiter and its circling orbiter—outside the solar system entirely—two spacecraft are gliding across interstellar space. They have crossed over the invisible boundary that separates our solar system from everything else, into territory untouched by the influence of the sun. People have seen much deeper into the universe, thanks to powerful telescopes that catch the light of distant stars. But this is the farthest a human invention has ever traveled. These hunks of gleaming metal and circuitry—they are the furthermost tangible proof of our existence.

The twin Voyager spacecraft took off in 1977, carrying scientific instruments and golden records stuffed with information. Millions of miles away, they still communicate with Earth. They still collect data. But they are aging.

The spacecraft, traveling in slightly different directions, weaken every year. Their thrusters, which keep them steady, are degrading. Their power generators produce about 40 percent less electricity than they did at launch.

An illustration of Nasa's Voyager spacecraft.

To keep the Voyagers going, engineers make some tough decisions from afar. They tell the Voyagers, in commands carried over radio waves, to shut down systems or switch to backups, rationing every single watt. They prepare for what may be the mission’s final years. “Someday we’re going to have to say goodbye,” says Candy Hansen, a scientist at the Planetary Science Institute who worked on the Voyager mission in the 1970s and 1980s.

But not yet. This summer, engineers instructed Voyager 2 to fire up a set of thrusters that the spacecraft hasn’t used since 1989. Thrusters help keep the spacecraft steady, and the ones Voyager 2 was using were deteriorating, which meant they had to fire more often, until the number of pulses became “untenable,” according to NASA. Without healthy thrusters, the spacecraft would lose its ability to keep its antenna pointed toward Earth, the point of communication between the spacecraft and its stewards back home. Voyager 1 made the same switch last year.

Planet Saturn, taken by Voyager 2.

Engineers also shut off a heating component that keeps one of Voyager 2’s instruments warm enough to function in the frigid cold of space. Turning off a heater buys the mission four watts, the same amount it loses in a year. After months of deliberation, scientists decided that sacrificing this instrument, which last year helped confirm that the spacecraft had left the solar system, was worth it. Unlike the others, this instrument can point only in certain directions.

Some other instruments have, incredibly, tolerated the loss of their heaters, sometimes for years. According to NASA, the temperature of the cosmic-ray instrument, the most recent target of rationing, has dropped to –74 degrees Fahrenheit (–59 degrees Celsius), far lower than what it withstood during testing on Earth. But it’s still collecting data and beaming them home.

Narrow-angle camera views of the planet Neptune taken from Voyager 2 spacecraft.

Heaters on instruments on both Voyagers will be next on the chopping block. Suzanne Dodd, the Voyager project manager at NASA’s Jet Propulsion Laboratory, says the team may someday be forced to turn off one of the engineering elements that help the spacecraft communicate with Earth. “If it does work, then we gain two more watts,” Dodd says. “If it doesn’t work, then we lose the mission.”

No one was thinking about interstellar space when the Voyager spacecraft were dispatched. Scientists and engineers had set their sights much closer to home: the other planets, arranged in a rare alignment that allowed the spacecraft to swing from one to the next. “The twin Voyagers, despite all the odds to the contrary, have been our accidental visitors to the beginning of the space between the stars themselves,” says Ralph McNutt, a longtime NASA scientist who still works on the mission.

Computer graphics of Voyager 2 spacecraft's mission to Neptune.

Both spacecraft reached Jupiter first, capturing the planet’s swirling filigree of storms in unprecedented detail. Voyager 1 bopped from there to Saturn. Scientists were particularly interested in the planet’s largest moon, Titan, which would turn out to be one of the most intriguing spots in the solar system and a potential home of extraterrestrial life. If Voyager 1 didn’t collect enough good data before moving on, Voyager 2 would be redirected to try again. But the flyby worked, allowing Voyager 2 to swoop past Saturn and on to Uranus and Neptune.

Engineers took their first energy-saving step not long after that. After the planets, there was little to photograph aside from a handful of distant stars, so engineers turned off the Voyagers’ power-gobbling cameras. Hansen, who worked on the imaging team, says that if engineers resurrected the cameras now, “it would literally kill every other instrument on the spacecraft.”

View of fiery moon Io taken by Voyager 1 spacecraft fr. a distance of about 500,000 miles.

Voyager 1 left the solar system in 2012, and Voyager 2 followed last year. They registered the shift; their scientific instruments detected significant changes in the cosmic environment around them. The touch of the solar wind, invisible particles that envelop the solar system in a protective bubble, had disappeared. Engineers had already shut down a few instruments years earlier. Those still operating today are designed to study the few detectable phenomena of interstellar space, like cosmic rays and magnetic fields.
NASA has asked scientists to study the possibility of a new interstellar probe, but no formal missions exist. For now, the Voyagers are it. And one day, engineers will come into work expecting to hear the faint pings from the spacecraft, messages that take hours—nearly a day, in Voyager 1’s case—to cross the expanse and reach ground-based antennas. They won’t hear anything, and they might not ever be able to decipher why.
It could be that the spacecraft, running without enough heaters, become so cold that the fuel lines freeze, cutting off the power that thrusters need to keep the antenna turned toward home. Or it could be that the transmitters, which send and receive signals, run out of power, a scenario Dodd predicts could happen in the 2020s. The invisible tether that has connected scientists and engineers to the spacecraft for more than four decades, always unspooling further, would run out at last. One or two instruments might still work. The Voyagers would keep chronicling their journey through the cosmos, making history with every mile, but they’d have no way of calling home.

Here are the four spots where NASA’s asteroid probe might land

Bennuu

NASA’s OSIRIS-REx spacecraft is currently hanging out around the asteroid known as Bennu. It’s been there for months, taking photos and scanning the asteroid’s surface to get a better idea of exactly what dangers the probe might face when it eventually touches down.

Now, after scrutinizing every square inch of the massive rock, NASA has narrowed down the possible landing sites to just four candidates. Each of the four spots is relatively inviting, with little in the way of large debris, but the science team still has some work to do before they can make the final call.

When the mission first launched, NASA believed things were going to progress faster than they have. When the probe arrived at Bennu it discovered that the asteroid is actually far more “messy” than anyone could have guessed, with debris scattered all over the surface. This has complicated the search for a suitable touchdown site.

The ultimate goal has always been to retrieve samples of the asteroid’s material and return it to Earth. Selecting where to grab that sample from is difficult due to the requirements of the sample-collection system on the spacecraft. The material has to be smaller than an inch or the probe won’t be able to grab it, but the four potential landing sites seem to offer suitable material.

“We knew that Bennu would surprise us, so we came prepared for whatever we might find,” OSIRIS-REx principal investigator Dante Lauretta said in a statement. “As with any mission of exploration, dealing with the unknown requires flexibility, resources and ingenuity. The OSIRIS-REx team has demonstrated these essential traits for overcoming the unexpected throughout the Bennu encounter.”

From here, the team will narrow down the selections to just two and then perform flybys of the locations to eventually select the sample collection site. That maneuver won’t actually come until later next year, and the flight back to Earth will take another three years, so we won’t actually get any asteroid bits from Bennu until late 2023 at the earliest.

NASA Has Closely Measured a Shockwave From The Sun For The First Time

Gigantic interplanetary shockwaves reverberate across our Solar System, originating from the Sun and the bursts of charged particles or solar winds escaping it. But measuring such a shock in detail takes some very finely tuned instruments – and scientists just managed it for the first time.

These shocks are made up of particles transferring energy through electromagnetic waves, rather than bouncing directly into each other – what's known as a collisionless shock.

Understanding how these shocks happen in Earth's vicinity could prove useful on a greater scale, since these types of shockwaves are also spewed forth by things like supernovae and even black holes.

The solar winds that give rise to interplanetary shocks come in two types: fast and slow (as you can probably guess, one of the key differences between them is their speed of travel). As a fast stream overtakes a slow stream, a wave is created, causing ripples that spread out across the Solar System.

It's thanks to NASA's Magnetospheric MultiScale satellites (MMS) that we've now been able to catch a shockwave as it propagates through space – because the four satellites that make up the MMS were only around 20 kilometres or 12 miles apart at the time, they were close enough to detect interplanetary shockwaves as they flashed by in just half a second.

"The [MMS] spacecraft obtained unprecedented high‐time resolution multipoint particle and field measurements of an interplanetary shock event," the researchers write in their paper.

In particular, the Fast Plasma Investigation instruments on board the MMS were responsible for taking the all-important readings – a suite of devices able to measure ions and electrons in space at up to six times per second.

The instrument detected two clumps of ions: one from the solar wind shockwave itself, and one pushed out of the way as the wave passed.

The team says this helps to explain how energy and acceleration gets passed on as these shocks travel; due to the relatively small scale of the area covered by the MMS, it was also able to pick up small scale irregularities within the shock.

More shockwave measurements should be within the capabilities of the MMS, the team behind the latest research says – not just strong interplanetary shocks, but also weaker and rarer ones, which scientists know less about.

And this is just the latest feather in the cap of the MMS: it's already been responsible for analysing how energy is dispersed when solar storms strike Earth's atmosphere, and for logging other key changes in our magnetosphere.

Haleakalā Crater, Maui, Hawaii, US

The spectacular sight of the first rays of the sun stretching over the horizon can be witnessed at the Maui landmark. Haleakalā or "House of the Sun," is a dormant volcano, and prior reservation is required to watch the sunrise.

Ultimately these interplanetary shockwaves contribute to the space weather that can have dramatic effects on our own planet – which is why scientists are so keen to learn more about them, not just to make new discoveries but to refine existing hypotheses. With the MMS readings, they now have their first close-up look.

"Studying [interplanetary] shocks at kinetic scales thus offers new test beds for our current understanding," say the researchers.

Asteroid 'the size of the Great Pyramid' to fly past Earth this month

Illustration of an asteroid. Even in the main belt the asteroid density is very low. On average, distances of millions of miles separate even the closest members. Most of them, as this artist's impression shows, are lone wanderers.

A huge chunk of space rock - which has been compared to the size of the Great Pyramid - will hurtle past our planet later this month.

But (despite reports from tabloid news outlets), it’s not time to head to the doomsday bunkers quite yet.

Yes, asteroid 2019 OU1 is fairly large (it’s thought to be 233ft to 524ft across), but it’s not a ‘planet killer’ or even a ‘city killer’.

It’s also going to miss us by a fairly large margin on August 28, shooting past at around 639,000 miles away (equal to two and a half the distance of the moon).

Asteroids, also referred to as minor planets, are small, rocky bodies floating mostly in the asteroid belt – between the orbits of Mars and Jupiter. They are mainly made of materials (metal or rock) left over from the formation of the inner solar system.

It's also nowhere near the size of the sort of 'planet killer' asteroid which killed the dinosaurs.

It’s not too much bigger than an asteroid which exploded over Chelyabinsk six years ago.

During the 2013 Chelyabinsk event, 1500 people were injured and 7300 buildings damaged by the intense overpressure generated by the shockwave at Earth’s surface.

Unesco demands answers from Peru over impact of new Machu Picchu airport

Unesco has sent a letter to the Peruvian government demanding information about the construction of a new airport near Machu Picchu and what impact it could have on the Inca citadel, the country’s biggest tourist attraction and a world heritage site.

The letter, which has not been made public, reminds Peru of its obligation to protect its world heritage sites and directly refers to Chinchero, the historic village in the Sacred Valley, near the town of Cusco, where the controversial new airport is being built – to the horror of archeologists.

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The missive insists that Peru must coordinate with Unesco, the United Nations’ cultural agency, on any construction that could affect Machu Picchu and Cusco’s historic centre, also a world heritage site. A spokesperson for Peru’s ministry of culture said it would reply by 25 August, the date set by Unesco to receive an official response.

It is not the first time Unesco has sent Peru a warning about Machu Picchu. It threatened to place the famous ruins on a list of world heritage sites in danger in 2017 over fears overcrowding could damage the structure.

As a result Peruvian authorities put controls on the flow of tourists – an average of 5,000 a day in summer, more than double the Unesco-recommended limit – by dividing visits to the site into morning and afternoon shifts. Around 1.5m tourists visited Machu Picchu in 2017 and visitor numbers continue to increase. The Peruvian government hopes a second airport for Cusco, with direct flights from Miami and Buenos Aires, could nearly double the number of tourists.

The Peruvian president, Martín Vizcarra, has vowed that the airport, set for completion in 2023, must go ahead. He used his recent Peruvian independence day speech to allay fears that the construction would affect the “archaeological, natural, historical and cultural legacy of Cusco”. On a visit to the site this week, Peru’s transport minister, María Jara, said “nothing would stop” the airport’s construction.

While tour operators and hoteliers mostly agree that Cusco, Peru’s principal tourist destination, needs a second airport, there is debate about whether the 600-year-old Inca site of Chinchero is the best location for it. Juan Stoessel, general manager of the Casa Andina hotel chain, argues the chosen location would allow planes to land and take off from both sides of the runway – unlike the alternative sites in the mountain region – making it a hub for flights from the main cities in the region.

“Cusco receives around 3.5m tourists a year, which is a very low number compared with other world-class tourist destinations,” said Stoessel, adding that nearby archeological sites such as Ollantaytambo, Choquequirao and Vilcabamba needed better management.

But Marisol Mosquera, founder and CEO of Aracari Travel, said: “It breaks my heart to see one of the most monumental and gorgeous landscapes in the Andes being defaced in the name of ‘progress’. Our goal was to promote sustainable, low-impact, high-quality tourism. Now the destination is being destroyed.”

A spokesperson for Unesco Peru said it could not comment as matters relating to world heritage sites were dealt with by the body’s Paris headquarters.

Jupiter’s Great Red Spot Is Behaving Strangely

If on a clear and starry night in mid-May you had trained a high-powered telescope on just the right part of Jupiter, you would have seen something very, very strange. The Great Red Spot, one of our solar system’s most famous features, would have appeared to be slowly unraveling. You would have seen the swirling storm system casting off ribbons of rose-colored gas like petals in the wind. It would have been beautiful.

Earlier this year, dozens of die-hard amateur astronomers across the globe began noticing that the Great Red Spot’s ordinarily ovoid figure looked distorted. By April, it seemed to be shedding red flakes. In May, that flaking grew so extreme that the spot looked as though it might disintegrate.

The amateur community, a tight-knit group that regularly communicates and shares photos over social media, was charged with excitement and anxiety. It had never seen anything like this before, and members worried what it might mean. On a warm Australian night in early May, the longtime amateur and software engineer Anthony Wesley was floored when his telescope captured an image of a bright streamer curling away from the spot. That, he thought, is not something you see every day.

Humans have been observing the Great Red Spot since the invention of the telescope in the 1600s, and at its peak, the storm was three times wider than the Earth. Since the late 19th century, though, it has been shrinking, slowly but steadily. In 2012, amateur astronomers noticed that its diminution had accelerated. And in May, when they saw it flaking, they feared that it might be on the verge of extinction.

“Are we seeing the ‘beginning of the end’? The GRS Death dance?” one astronomer wondered aloud in a Facebook group for Jupiter enthusiasts. “I was scared because if the Great Red Spot disappears … it’s like you go to New York and remove the Statue of Liberty,” another told me.

As it has shrunk, the storm has also grown darker, redder, and taller; this year, the color palette is more intense than ever, according to a NASA press release accompanying new photos of Jupiter taken by the Hubble Space Telescope. Through all those changes, though, the spot’s position has never shifted: Twin jet streams circle the planet in opposite directions and lock the storm in place. Moving at speeds approaching 400 miles an hour, the jets constantly bombard the spot with clouds and vortices; some incorporate themselves into its body, while others pass through unhindered. The whole system looks something like a wristwatch wrapped around the planet, with the jet streams for a band and the spot for a face.

Hubble Space Telescope

In the months after they first recognized the spot’s unusual behavior, the amateurs around the world monitored it at virtually all hours of the day and sent their images to the scientists at NASA’s Outer Planet Atmospheres Legacy program. The storm looked to have undergone a sudden contraction (though more recent amateur data suggest it has since returned to its former size). But when the scientists analyzed its behavior using the amateur images along with the higher-resolution Hubble photos, they arrived at a very different story.

The Great Red Spot was not dying—at least not any faster than it had been before. To the amateurs, it had looked as though strands of the storm were tearing away. But according to Amy Simon, who leads the Outer Planet program, that impression resulted from the fundamental imprecision of visual measurements.

Recently, Simon told me, the program has started measuring the storm using its dynamics instead of its visual features. Tracking the storm’s velocity rather than its color revealed that much of the red gas that had seemed to be flowing out of the Great Red Spot was actually flowing in. This, she said, is nothing new.

“It’s always doing this,” Simon told me. The Great Red Spot “is always pulling stuff in and parts of it are flying off. That is not unusual at all.” The difference this time, she said, has to do with both the appearance and the behavior of those mysterious red flakes.

For starters, the material flowing into and around the red spot has taken on a reddish color more like the storm’s, creating the illusion of shedding. Simon told me that shift in color occurs before the material ever reaches the storm, while Glenn Orton, a scientist at the NASA Jet Propulsion Laboratory, thinks the shift happens later.

Either way, the material’s unusual movements have only enhanced the illusion. Typically, Simon explained, material from the jet streams either integrates into the storm or passes clean through. In recent months, though, it has been noncommittal at times, circling the periphery of the storm a few times before escaping its orbit, as though going for a quick carousel ride. That outer circuit, Orton says, has “gone from a two-lane country road … to a six-lane highway.” The ribbons of gas torn from the storm may never really have been part of it at all, more commuters than inhabitants.

Taken together, these findings offer a clear answer to the mystery of why the Great Red Spot is disintegrating: It isn’t. But with that simple answer comes a new mystery just as perplexing as the first: If it wasn’t disintegrating, why did it look like it was? As is often the case with the workings of the Great Red Spot, scientists don’t yet have an explanation.

For now, Simon told me, they must simply accept much of Jupiter’s behavior as random. By investigating the recent changes, though, some scientists hope to find clues to perhaps the planet’s greatest mystery of all: why the Great Red Spot is red in the first place.

Tim Dowling, an atmospheric-physics professor at the University of Louisville, views the recent disruptions as a chance to test scientific models explaining the spot’s color. Many of its observers have hypothesized that it may grow redder at higher altitudes, but the specific mechanics of what is turning red and how remain open to interpretation. Simon sees a few possible explanations. Dowling favors the crème brûlée model, so called because it posits that the spot’s color comes from a thin coating of solid particles atop a bed of clouds, just as the burnt crust of a crème brûlée sits atop the custard.

When I asked Anthony Wesley about Simon’s account of the Great Red Spot’s behavior, he was skeptical, though he freely acknowledged that, given the ambiguity, I might be better off taking Simon and her colleagues at their word. And yet he knew what he had seen with his own eyes—parts of the spot spinning out and away. Wesley’s way of looking at the cosmos is distinct from NASA’s, and the discrepancy in their accounts reflects that. Judging by the velocities Simon measured in her data, the storm system isn’t contracting any faster than it has been in recent years. And judging by the images Wesley and the other amateurs captured, the red oval we see when we look up at Jupiter through a telescope shrank considerably before returning to its former size.

If, somehow, the Great Red Spot faded from view but the storm spun on, would it still be the Great Red Spot? The underlying system, in Simon’s words, would be the same. But if Wesley awoke in the middle of the night to find that the cosmic phenomenon he’d spent more than 15 years photographing had vanished from sight, that fact might come as little consolation.

Earth's Last Magnetic Pole Flip Happened Much More Slowly Than We Thought

Earth's protective shield.

New research suggests Earth's most recent magnetic field reversal took longer to complete than previously thought: around 22,000 years in total. Figuring out why this particular flip was so drawn out will let us better understand this mysterious process, and maybe even help us to prepare.

It's a fact geologists know about our planet: every few hundred thousand years or so, Earth's magnetic field quite literally flips – so the magnetic north is at the South Pole, and vice versa. It's important to establish the timings of these reversals so we know how much of a window we have to potentially adapt for the next one.

With so many modern-day systems like GPS reliant on knowing north from south, a flip could easily cause chaos one day.

Earth's magnetic field is created by the planet's liquid iron outer core spinning around its solid inner core. Charting magnetic field reversals back through time isn't easy, but clues can be found in ocean sediments and lava flows that lock in the direction and the strength of the magnetic field at the time they emerged.

"Lava flows are ideal recorders of the magnetic field," says geologist Brad Singer, from the University of Wisconsin-Madison. "They have a lot of iron-bearing minerals, and when they cool, they lock in the direction of the field."

"But it's a spotty record. No volcanoes are erupting continuously. So we're relying on careful field work to identify the right records."

Singer and his colleagues looked at lava flow records from Chile, Tahiti, Hawaii, the Caribbean and the Canary Islands, looking at the timing of the most recent reversal. Named the Matuyama-Brunhes reversal after the scientists who discovered magnetic field flips, it happened about 770,000-780,000 years ago.

Researchers Rob Coe and Trevor Duarte at work in Haleakala National Park, Hawaii.

That timing suggest we're 'overdue' for a reversal right now – although we may just be in a period of instability that doesn't result in a full flip (something that's happened before, too).

There's currently some debate over how long the next reversal will last.

Based on the lava rock records, the researchers found that the main part of the Matuyama-Brunhes event lasted 4,000 years, but was preceded by 18,000 years of instability and excursions (those temporary, partial reversals).

The findings were backed up by an analysis of rocks from the ocean floor, a more continuous but less precise record of Earth's magnetic field.

This time frame is longer than previous estimates and hints that we won't suddenly be surprised by a relatively quick flip.

We still don't know for sure how long the next flip might last – or exactly when it's coming – but we do now have a wealth of extra data to help scientists make their best estimations. If we're in for another Matuyama-Brunhes reversal, this study suggests it's going to last for many generations.

When the time does come, our planet's magnetic field is going to be weaker and more complicated than it is now, so it's vital that we're prepared.

"Reversals are generated in the deepest parts of Earth's interior, but the effects manifest themselves all the way through the Earth and especially at Earth's surface and in the atmosphere," says Singer.

"Unless you have a complete, accurate and high-resolution record of what a field reversal really is like at the surface of Earth, it's difficult to even discuss what the mechanics of generating a reversal are."