Why a Japanese spacecraft is firing a bullet into an asteroid

 About 180 million miles from Earth lies a tiny asteroid called Ryugu, with a diameter of roughly 0.6 miles, orbiting the sun once every 16 or so months. If everything goes as planned, we’ll be firing a bullet straight into the rock today—all in the name of scientific study.

03 October 2018, Bremen: Hansjörg Dittus (l-r), Member of the Executive Board of the German Aerospace Center (DLR), Pascale Ehrenfreund, Chairman of the Executive Board of the German Aerospace Center (DLR), Hiroshi Yamakawa, President of Japan Aerospace Exploration Agency (JAXA), and Jean-Yves le Gall, President of the International Astonautical Federation (IAF), are at the 69th International Astronautical Congress IAC at the press conference on the landing of the lander 'Mascot' on the asteroid Ryugu. The 'Hayabusa2' probe of the Japanese space agency JAXA has brought the lander to the asteroid. The German Aerospace Center has developed and built 'Mascot' in collaboration with the French Space Agency CNES. Photo: Mohssen Assanimoghaddam/dpa

Scientists have been preparing for this for nearly a decade now. In 2014, Japan’s space agency, JAXA, launched Hayabusa-2, a robotic spacecraft designed to study Ryugu up close and help us learn more about the structure and composition of asteroids in the solar system. The spacecraft arrived at Ryugu in June, keeping pace with the asteroid’s orbit around the sun.

Hayabusa-2 is, without a doubt, one of the wildest missions space scientists and engineers have ever attempted. The spacecraft is armed with multiple instruments collecting images and data across a host of different spectrums. A key goal is to deploy four different rovers, three of which were sent to the surface last fall and provided our first glimpse of a very vibrant Surface.

This computer graphic image provided by the Japan Aerospace Exploration Agency (JAXA) shows the Japanese unmanned spacecraft Hayabusa2 approaching on the asteroid Ryugu. Hayabusa2 is approaching the surface of an asteroid about 280 million kilometers (170 million miles) from Earth. The JAXA said Thursday, Feb. 21, 2019 that Hayabusa2 began its approach at 1:15 p.m

And then there are the sample returns, which take the audacity of the mission to a whole other level.

On Thursday, the spacecraft will descend towards the surface of Ryugu and touch down with a sampling horn.

Once the spacecraft makes contact, it will literally fire a 5-gram metallic bullet into the rock, at a speed of over 670 miles per hour.

The horn’s catcher will collect as much of the ejected, grainy debris as it can (the microgravity environment of the asteroid will help make this more feasible than you might think). And then Hayabusa-2 will perform this shot yet again and collect more material. The goal is to gather actual material of the asteroid itself, and bring it back to Earth for more detailed study in the lab.

A close-up of the asteroid Ryugu, from which the Japanese space agency will extract pristine rock samples.

And that's not all: A second sample return attempt will take place later in the spring, which involves using explosives to create a six-foot-long crater in the surface of the Ryugu and collect subsurface rock to bring back home. Yowza.

Why go to such explosive lengths? Although some people hope an analysis of this rock can tell us more about prospecting asteroids for resources in the distant future, most scientists are focused on using the Ryugu sample to learn about the origins of the solar system.

Along with OSIRIS-REx (another mission focused on the study and sample return of a near-Earth asteroid), Hayabusa-2 has the potential to finally provide a better glimpse into the early days of our solar system, and how this may have laid the groundwork for the beginnings of life on Earth.

Most of what we know right now about the formation of the solar system comes from meteorites that have impacted the Earth over its 4.5 billion-year lifespan. We’ve learned a ton from rigorous analyses of these materials, but our understanding is still limited to things like how contaminated these rocks get as they pass through the atmosphere and hit the dirt, or how they fracture and turn quickly into dust.

This Oct. 25, 2018, image provided by the Japan Aerospace Exploration Agency (JAXA) shows asteroid Ryugu. Japanese spacecraft Hayabusa2 is approaching the surface of an asteroid about 280 million kilometers (170 million miles) from Earth. The JAXA said Thursday, Feb. 21, 2019, that Hayabusa2 began its approach at 1:15 p.m. Hayabusa2's shadow is seen at center right over Ryugu

Orbiter missions that study asteroids in space through remote sensing techniques add new insights, but given pictures can't be subject to physical or chemical studies, imaging can only tell us so much about what these rocks are made of or how they formed. That's why sampling, however audacious, holds so much promise.

“What the sample return really tells us, is that we know where the asteroid comes from, we have pictures of it, and we have this sample that has not been contaminated by other factors,” says Michael Nolan, head of the OSIRIS-REx science team at the University of Arizona. And there's nothing quite like an intact, pristine piece of a rock that has been virtually untouched for billions of years.

JAXA’s initial Hayabusa mission was the first successful sample return from a near-Earth asteroid, but can only be considered a partial success, since those samples were really more like particles, collected from an asteroid composed of a volcanic kind of rock, during a mission sagged by obstacle after obstacle.

Nevertheless, the tiny specks of dust returned from that mission helped us to learn about the timeline and history of some rocks in the solar system, particularly ones that reside outside the asteroid belt. H2 will look to take things a step further.

03 October 2018, Bremen: Hansjörg Dittus (l-r), Member of the Executive Board of the German Aerospace Center (DLR), Pascale Ehrenfreund, Chairman of the Executive Board of the German Aerospace Center (DLR), Hiroshi Yamakawa, President of Japan Aerospace Exploration Agency (JAXA), and Jean-Yves le Gall, President of the International Astonautical Federation (IAF), are at the 69th International Astronautical Congress IAC at the press conference on the landing of the lander 'Mascot' on the asteroid Ryugu. The 'Hayabusa2' probe of the Japanese space agency JAXA has brought the lander to the asteroid. The German Aerospace Center has developed and built 'Mascot' in collaboration with the French Space Agency CNES. Photo: Mohssen Assanimoghaddam/dpa

Nolan explains that Ryugu is a more primitive rock than ones we’ve studied before, rich in carbon and replete with a sort of gemstone facade. This is distinct, too, from Bennu, the asteroid at the center of the OSIRIS-REx mission that will also attempt an asteroid sample return. “We’re going to get two very different pieces of solar system history,” says Nolan.

These samples could help us glean a ton of insights when it comes to how asteroids could be used as a vessel for transporting organic and inorganic materials alike across different worlds. In other words, we might learn more about whether asteroid impacts seeded the early Earth with the types of ingredients necessary for life to later evolve.

But first, we have to collect those samples. Hayabusa-2 will finish up its work through the year and depart Ryugu in December, returning back to Earth and delivering its samples later in 2020. Let’s hope today’s attempt doesn’t end up backfiring (ha, get it?) The operation is set to take place at 6:00 p.m. Eastern Time, and JAXA will broadcast the entire thing live (with an English Translation) from its control room.

Meet the newest known moon of Neptune

In 1989, Voyager 2 flew by Neptune, right, and spotted six small inner moons, represented in the composite at left. A tiny moon between Proteus and Larissa went undetected at the time, but Mark Showalter discovered the moon in 2013 using the Hubble Space Telescope and has now officially named it Hippocamp

For billions of years, a small moon orbiting the ice giant Neptune hid amid the dusky starlight. Now, the minuscule world has a name—and scientists are beginning to piece together its violent history.

“It was just incredibly difficult to detect,” says the SETI Institute’s Mark Showalter, who first spotted the moon in 2013 and describes it today in the journal Nature. The newly described satellite brings Neptune’s clutch of known orbital companions up to 14. A diver, Showalter named the tiny moon Hippocamp after the mythological beast that gave rise to the genus name of one of his favorite aquatic creatures: seahorses.

“When it came time to pick a name out of Greek and Roman mythologies from the seas, it was like, Oh, that’s not a hard one,” he says.

The hardest part was finding the small moon in the first place. Nestled relatively close to Neptune and just 21 miles wide, the rocky object is small enough to fit within the narrowest portion of the English Channel. Finding it took several years of careful scouring through pictures from the Hubble Space Telescope.

“You can only find these [moons] because folks like Mark Showalter have figured out how to wring every last photon out of those images,” says Heidi Hammelof the American Universities Research Association.

Not necessarily intending to go moon-hunting, Showalter happened upon the small world after developing a new way to search for faint structures around Neptune. He and his colleagues had aimed Hubble at the planet in 2004, 2005, and 2009 hoping to get a good look at the bizarre ring fragments arcing around the big blue planet. Because those arcs are so feeble, the team stacked long-exposure Hubble images atop one another, which amplifies the telescope’s sensitivity. (See how an Earth-bound telescope found a strange giant storm on Neptune.)

Then, Showalter decided to use the technique to look for moons.

One by one, he spotted Neptune’s known inner moons Proteus, Thalassa, Galatea, Despina, Larissa, and Naiad, a moon that hadn’t been seen since the Voyager 2 spacecraft cruised by in 1989. Yet there, among those faraway worlds, was an interloper—a faint point of light behaving just as a moon would, except that no one had seen it before.

After tracking the spot’s motion, Showalter and his colleagues were satisfied that they’d stumbled upon an actual moon and not just a camera artifact; based on its brightness and on data from another observing campaign in 2016, they estimated its size. As for what it’s like?

“The truth is, it’s a dot,” Showalter says.

A history of cometary violence

More puzzling, perhaps, is Hippocamp’s orbit, which is jammed up against that of Proteus, the largest of Neptune’s inner moons. The two are so close—roughly 7,500 miles apart—that it’s unlikely Hippocamp randomly ended up there.

Instead, Showalter suspects that it formed after a comet slammed into Proteus and launched shrapnel into orbit around Neptune. Eventually, that debris clumped together into a new moon. If this scenario is true, Hippocamp’s birth is probably recorded in the form of a giant Protean crater called Pharos.

But that wasn’t its only experience with violent impacts. Since then, it’s possible that comets have broken Hippocamp apart multiple times, essentially putting it through a blender that jumbles the moon’s materials and turns it into a transient ring. (Find out why astronomers think Saturn’s famous rings may be surprisingly young.)

“It’s in a place around Neptune where you’re far enough away that when you break something apart, it’ll eventually form back into the moon,” Showalter says. “A lot of the inner moons of Jupiter, Saturn, Uranus, and Neptune have probably broken apart multiple times over their history.”

But telling the detailed stories of Hippocamp and other objects at the fringe of the easily observable solar system requires an instrument much sharper than Hubble, or a spacecraft sent into the deep.

“You can find them with Hubble,” Hammel says. “But you cannot take it to the step of trying to understand the detailed geology, the detailed chemistry of the objects out there at the edge of the solar system.”

Why our blue planet is getting greener

Why is the Earth growing greener?

 The blue planet is going green—literally. Since the 1980s, satellite images have shown that leafy cover across the globe has grown by 2.3 percent per decade.

 A new study, published February 11 in Nature Sustainability, helps explain why. One main driver is the “fertilization effect,” brought about by humans burning fossil fuels. As CO2 increases in the atmosphere, this boosts photosynthesis—as long as water, light, and nutrients are not limited. When plants take up more of the gas, they produce more food and unfurl new leaves.

 But researchers also found another cause for the change in hue: planting more crops and trees. China and India, the two most populous countries on Earth, have contributed about a third of the greening seen since 2000, mainly in the form of forests and farms.

Green coverage World

 In this most recent paper, scientists at Boston University took a closer look at this greening trend. They used data from NASA’s Moderate Resolution Imaging Spectroradiometer, or MODIS, which uses advanced satellite technology to document the Earth’s surface on a near-daily basis. In images spanning from 2000 to 2017, the researchers looked at the change in greenness in plant-covered regions, as well as the what the underlying land uses were—including croplands, forests, and grasslands.

 The satellite data revealed that globally, one-third of vegetated areas are greening, while only five percent are browning. “Human land use management in many regions is more important than those indirect factors [of climate change and CO2 fertilization],” says Chi Chen, lead author of the study. “China and India, two developing countries, contribute the most in the increase in leaf area.” According to the study, the two nations contributed more greening relative to their plant-covered area than other countries.

 While only 6.6 percent of the world’s vegetated area is in China, the country is responsible for 25 percent of the increase in global greening. The study found that most of China’s greening occurred in its forests, with croplands also contributing. Since the early aughts, China has implemented large-scale programs to protect and restore its wooded lands.

In India, agricultural fields accounted for 82 percent of greening. Food production has increased in both countries, with fertilizer use and irrigation helping farmers harvest more from the same acreage.

“CO2 fertilization and climate change are still important,” says Chen. Extra CO2 in the atmosphere is still responsible for the majority of the change in greenness seen in the 17-year period he and his team looked at. However, the study reveals that how we are managing forests and croplands has a greater impact that previously thought.

The findings could complicate how scientists use computer models to study the Earth. While CO2 fertilization is relatively easy to express in equations, Chen says, “human land use is kind of random and hard to predict.”

It’s unknown how long the Earth will continue to green, but there are signs it won’t last. In fact, a recent study found that as the planet warms and its soil dry, plants will be starved of water, leading to a drop-off in plant growth.

“The competition between different fluxes [of carbon] is hard to know,” says Chen. But his finding on the importance of human land use gives scientists “a direction to focus on” in future work.

The Surprising Reason Zebras Have Stripes

Are you sure this is a zebra?

For Tim Caro, it was surprisingly easy to dress horses like zebras. Several vendors were already selling coats with black-and-white stripes, often as fun gimmicks. But, as Caro learned, such coverings have an unexpectedly serious effect. “There are enormous benefits to having a striped coat for a horse,” he told me.

Caro, a biologist at the University of California at Davis, has spent years thinking about why zebras are striped, and has even written a book about this mystery. In his latest bid to get clear answers, he and his colleagues traveled to Hill Livery, a stable in southwest England that keeps several captive zebras alongside domestic horses.

By comparing these two species, as well as horses that were comically cloaked in zebra-striped coats, the team found fresh evidence for what Caro thinks is the only plausible explanation for the striking stripes: They evolved to deter bloodsucking flies.

Zebras stay in a snow-drifted enclosure at the Kyiv Zoo, Kyiv, capital of Ukraine, December 4, 2018. Ukrinform. KYIV. The story of the Kyiv Zoo begins on March 21, 1909 when local enthusiasts received a permission to rent land and raise money for animals. In April 1914, the rich collection of animals and birds was moved to Shuliavka suburbs opposite the famous Kyiv Polytechnic Institute. Sixteen acres were not suitable for housing, but the hilly landscape and deep ravines were perfect for the new inhabitants. Throughout its long history the Kyiv Zoo experienced hardships during WWI and WWII, but it always bounced back becoming home to yet more species. As of today, the Kyiv Zoo is a favourite weekend destination for locals and a must-see site for tourists

Scientists have been puzzling over the role of zebra stripes for more than 150 years. But, one by one, the most commonly proposed explanations have all been refuted. Some researchers have suggested that the stripes act as camouflage—they break up zebras’ outlines or resemble fields of tree trunks. But that can’t be true: Amanda Melin of the University of Calgary recently showed that lions and hyenas can’t even make out the stripes unless they get very close. 

Another hypothesis says that the black stripes heat up faster than the white ones, setting up circulating air currents that cool the zebras. But a recent study showed that water drums cloaked in zebra pelts heat up just as much as those covered in normal horse skins.

That leaves the fly idea. When it comes to biting insects, zebras are doubly cursed. For one, they’re highly susceptible to a variety of fatal diseases, including trypanosomiasis, African horse sickness, and equine influenza, that are spread by horseflies and tsetse flies. They’re also very vulnerable to insect attacks: Compared with other grazers such as antelopes, the hairs on their coat are unusually short, allowing flies to more easily find blood vessels with their piercing mouthparts.

Zebras are seen at the Nairobi National Park, near Nairobi, Kenya, December 3, 2018.

Stripes, for some reason, seem to help. In 2014, Caro and his colleagues showed that striped horses—three zebra species and the African wild ass with thin stripes on its legs—tend to live in regions with lots of horseflies. And several researchers, over the years, have shown that these flies find it hard to land on striped surfaces. No one, however, had watched the insects trying to bite actual zebras. That’s why Caro’s team went to Hill Livery.

By watching and filming the stable’s horses and zebras, the team confirmed that horseflies were much worse at alighting on the latter. The flies had no problem finding the zebras or approaching them, but couldn’t stick the landing. “You get a quarter as many landings,” Caro said. “The flies just can’t probe for a blood meal with the zebras.”

The team found the same trend when they put striped coats on the horses. Cloaked in stripes, the very same animals suddenly became more resistant to flies, except on their uncovered heads. And uniformly colored coats had no effect; the stripes, specifically, befuddled the flies.

One of the two Grevy's zebras born recently at Edinburgh Zoo, with its mother.

“When we looked at the videos, we found that the flies simply aren’t decelerating when they come in to the stripes,” Caro said. Either they miss and overshoot the zebras, or they bump into the hides and bounce off. Something’s clearly throwing them off, but the details are still a mystery. Caro said that they might treat the black stripes like a pair of trees, try to fly between them, and end up colliding with the white stripes. Alternatively, the stripes might mess with their optic flow—their sense of objects moving across their visual field.
Paloma Gonzalez-Bellido of the University of Minnesota, who studies insect vision, favors the latter idea. These insects use optic flow to gauge their own speed and their distance from nearby objects. “I think that the key is that the stripes’ thickness and orientation is not consistent, either within a stripe or across them,” she says.

“This is probably what makes it difficult for the flies to control their landing.” (She also notes that cuttlefish use their color-changing skins to create striped patterns that move across their bodies, and these “passing clouds” might also work by disrupting the optic flow of their prey.)

If Gonzalez-Bellido is right, a more evenly striped coat should offer less protection. Caro’s team is now planning to test this hypothesis, and others. “Now that we know striped coats work just as well as stripes on real zebras, we can really play around with them,” he said. “We can put on coats with very wide stripes, or different orientations, or gray stripes. We can see how those affect fly behavior.”

In the meantime, he is wary of making firm recommendations to the equine industry. “I wouldn’t want to suggest that horse-wear companies sell striped livery for their riders yet,” he said. “We need to do the work first.”

More important, I ask him, Would a striped shirt protect me from biting flies? “I’ve been very cautious about saying that until we got these results, but now I’m not so sure,” he said. “I think that a striped T-shirt might work very nicely.”

What would happen if one of Antartica's biggest glaciers collapses?

The Thwaites Glacier is one of the most dangerous glaciers in the world, and scientists are eager to travel to Antarctica to study it.

NASA researchers released a study in January that said a giant cavity roughly two-thirds the size of Manhattan was rapidly melting underneath the glacier due to climate change. The cavity is big enough to have contained 14 billion tons of ice, with most of it melting over the last three years. 

 Even before this cavity, Thwaites' rapid ice loss and potential impact on global sea levels was significant enough that researchers from around the world planned to physically travel there starting this year.

Only 28 people have ever set foot on the glacier, according to Britain's Natural Environmental Research Council, or NERC.

So what might happen if Thwaites does collapse?

"It could potentially destabilize the whole region of west Antarctica," Lucas Zoet, a University of Wisconsin geoscientist, , told USA TODAY.

Thwaites is a 'wildcard' for sea levels

The glacier sits in west Antarctica and flows into the Amundsen Sea. Roughly the size of Florida, Thwaites' melting is currently responsible for about four percent of global sea level rise, according to NASA in its recent study on the glacier's giant hole.  

"It's a major throughway of how ice gets discharged from west Antarctica into the ocean," said Zoet.

Thwaites has been difficult to study because it's far from U.S. bases in the Antarctic and also because the weather is "particularly bad," said Zoet.

The glacier measures more than 70,000 square miles, making it one of the largest glaciers in the world, said NERC.

The glacier's grounding line, the point at which ice meets the land underneath, has retreated over 9 miles between 1992 and 2011, according to NERC. As ice and warmer sea water flow underneath the glacier, it lifts off the land and speeds up its retreat.

"If this cavity grows or sort of expands, that’s one way it can get off this last sort of ridge that Thwaites Glacier is hanging on to," Zoet told USA TODAY.

What especially worries scientists is if the melting accelerates. If all the ice on Thwaites is lost, it would raise ocean levels another two feet, according to the NASA study. But the glacier also backstops neighboring glaciers. If those glaciers also melt, sea levels could rise an additional eight feet, researchers warn. 

"It holds a kind of wildcard for being able to increase the rate of sea-level rise quite rapidly if things unfold a certain way," said Ted Scambos, a senior research scientist with the National Snow and Ice Data Center.

How do you visit a location so remote?

Scambos said research into Thwaites' retreat started as early as the 1990s, as satellite data got better at tracking Antarctic ice sheets.

Scambos is part of the International Thwaites Glacier Collaboration (ITGC), a partnership between British and American scientists that studies the glacier's retreat up close.

"Satellites show the Thwaites region is changing rapidly, but to answer the key questions of how much, and how quickly sea-level will change in the future, requires scientists on the ground with sophisticated equipment collecting the data we need to measure rates of ice-volume, or ice-mass change," said William E. Easterling, assistant director for the National Science Foundation’s Geosciences Directorate, in a statement last year.

Dire projections

"The point is not so much is whether or not it’s going to happen, unless we really change how much heat-trapping gasses we’re putting in the atmosphere," said Scambos of the glacier's melting. "Eventually, we’re going to lose big areas of the Antarctic, big areas in Greenland. The important thing is how fast is this going to happen."

Melting from Greenland and Antarctica would not only bump up sea levels, but might bring more extreme weather and dramatic shifts in temperature, according to a study published in Nature in February.

Scambos said coastal cities in the U.S. and worldwide are looking ahead to how higher sea levels could impact them. If Thwaites' melting happens over centuries, then nations would have more time to get ready.

 A faster rise in sea level, however, could force countries to act more urgently.

If that pace were to double or triple suddenly because glacier melt really picked up, "then that’s going to really throw a wrench into the ability for these nations to plan and prepare for the impacts of sea-level rise," Scambos said.