By Mike Wall  

Hayabusa2 will zoom by the asteroid 2001 CC21 in 2026, if all goes according to plan.

An artist's depiction of the Hayabusa2 spacecraft after inserting its capsule into Earth's atmosphere for sample delivery.

(Image: © JAXA)

Hayabusa2's first extended-mission destination is the roughly 2,300-foot-wide (700 meters) asteroid (98943) 2001 CC21, which the probe will fly by at high speed in 2026, if all goes according to plan. A more in-depth rendezvous with yet another space rock, 1998 KY26, is scheduled to follow in 2031. (Hayabusa2 won't collect any samples from 2001 CC21 or 1998 KY26.)

1998 KY26 is thought to be just 100 feet (30 m) or so wide — much smaller than both 2001 CC21 and Ryugu, which has a diameter of about 3,000 feet (900 m). The mechanical properties and other characteristics of such small asteroids aren't well understood, nor is the role that their collisions with Earth have played in our planet's history. So studying 1998 KY26 up close will yield valuable insights, Hayabusa2 team members said. 

"It is expected that the world’s first proximity observation of celestial bodies less than 100m in diameter will provide useful information, not only for elucidating the history of the Earth but also for planetary defense," team members wrote in a Hayabusa2 briefing document this past September.

Hayabusa2 will perform other tasks during this extended mission as well, including observing exoplanets and the zodiacal light — the faint glow in our solar system caused by sunlight bouncing off interplanetary dust. (You can read much more about the extended mission and its goals in the briefing document.)

The next decade-plus won't be just about the extended mission, of course. Hayabusa2 scientists have only just begun to assess and characterize the 0.19 ounces (5.4 grams) of pristine Ryugu material that landed in the Australian Outback last month.

A full investigation of this cosmic dirt and gravel could reveal key insights about the early solar system and, perhaps, the role that carbon-rich asteroids like Ryugu played in the rise of life on Earth, Hayabusa2 team members have said. Such work will involve scientists around the world — the mission team will loan some samples out — and almost certainly take decades. After all, researchers are still studying the 842 lbs. (382 kilograms) of moon material that NASA's Apollo program brought home between 1969 and 1972.

• Related: We may be in a 'golden age' of sample-return space missions

Hayabusa2 — the successor to the original Hayabusa mission, which delivered a few grains of material from the stony asteroid Itokawa to Earth in 2010 — launched in December 2014. It arrived at Ryugu in June 2018 and studied the space rock in depth for nearly a year and a half, dropping several hopping rovers and a microwave-sized lander onto the asteroid over that stretch.

Hayabusa2 left Ryugu in November 2019, successfully delivering the return capsule a little over a year later. Less than two weeks after that landing, on Dec. 16, China's Chang'e 5 mission aced its own cosmic delivery, returning fresh moon samples to Earth for the first time since the Soviet Union did so in 1976.

And there's even more sample-return action coming in the relatively near future. In October 2019, NASA's OSIRIS-REx mission collected a big sample from the carbon-rich asteroid Bennu. This material will touch down in Utah in September 2023, if all goes according to plan.

• Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook. 

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By Kasandra Brabaw 

A new "transforming" rover in development at NASA will be able to explore rough terrain unlike any rover before it. 

DuAxle (short for dual-Axel) gets its name because it’s made of a combination of a pair of two-wheeled Axel rovers. The Axel rover is a simple, two-wheeled rover with a long tether that connects to a larger vehicle and stabilizes the rover as it descends into and explores craters that other rovers would not be able to handle. The Axel is equipped with a robotic arm that can collect samples, as well as  stereoscopic cameras to gather imagery. 

DuAxel combines two of these innovative rovers, with the back end acting as an anchor and the front end detaching to explore rough terrain. When DuAxel finds a crater, pit, scarp, vent, or other extreme terrains, it can stop, lower its chassis and anchor itself to the ground before separating into two parts. The back half of the rover stays put and the front half separates, using a  long tether to stay connected to its anchor and maintain stability while exploring. The front half can then be reeled back in when it's finished. 

• Red Planet Express: 10 Ways Robots Move on Mars

Last fall, engineers from NASA’s Jet Propulsion Laboratory put the rover to a test in the Mojave Desert. "DuAxel performed extremely well in the field, successfully demonstrating its ability to approach a challenging terrain, anchor, and then undock its tethered Axel rover," Issa Nesnas, a robotics technologist at JPL, said in a NASA statement.

Axel, the front half of the rover, managed to maneuver around steep and rocky slopes just as the team expected. 

While the two-wheeled Axel offers greater flexibility in exploration, the traditional four wheels on a space rover are essential for traversing large swatches of land in a short amount of time. And so, Nesnas and his team began developing a version of Axel that could be tethered to a lander. But, they soon learned that tethering to a lander created the great disadvantage of having to be incredibly accurate in landing precision. The Axel rover would have to be within propelling distance from the crater scientists wanted to explore. 

And so, DuAxel was born. “The key advantage of DuAxel is made clear when you have landing site uncertainty, such as we do on Mars, or you want to move to a new location to rappel and explore with Axel,” Patrick Mcgarey, a robotic technologist at JPL and DuAxel team member, said in NASA’s statement. Essentially, he said, DuAxel is a transforming robot made for planetary exploration. 

While DuAxel was mainly created with Mars in mind, the robot opens access to many more extreme terrain that hasn’t yet been explored in the solar system — possibly the moon, Mercury, and even some icy worlds like Jupiter’s moon Europa, Nesnas said. 

Laura Kerberr, a planetary geologist at JPL, said she finds the Axel rover to be "quite delightful." Instead of safeguarding itself against dangers like falling or flipping over, as previous rovers have done, DuAxel is designed to withstand them.

The rover hasn’t yet been put to the test in space, but is currently waiting to be assigned a destination. As they wait, the DuAxel team continues to hone and update its technology. 

• Follow Kasandra Brabaw on Twitter @KassieBrabaw. Follow us on Twitter @Spacedotcom and on Facebook.

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By Leonard David 

A major asteroid or comet strike could cause extensive devastation and profoundly affect life on Earth.

Target Earth: This illustration shows a space rock approaching Earth, perhaps headed for destructive impact on our world.

(Image: © DoD)

Space.com: What's the impact of the Dec. 1 loss of the Arecibo Observatory's 305-meter telescope on your planetary radar efforts for NEO observations?

Johnson: The National Science Foundation made the hard decision that it needed to be decommissioned for safety reasons and brought down. But the telescope decided to do it on its own. Its planetary radar observation isn't unique, as we have it at our Goldstone [Solar System Radar in California's Mojave Desert] too. What was unique about Arecibo was the size of the dish and the power it generated, which gave it a longer range than we have at Goldstone.

Space.com: So we have lost capability?

Johnson: We have lost that capability, but we haven't lost planetary radar capability. But it does make Goldstone a more critical capability for us than it was. We did have some overlap and redundancy prior to loss of Arecibo, but now we have Goldstone. I think not only NASA but other agencies as well will soon engage in a study of what is the future for our planetary radar capability. I think the loss of Arecibo will provide the incentive to get that together, a concerted effort on the part of several agencies.

• Related: Potentially dangerous asteroids (images)

Space.com: How is the launch next year of NASA's Double Asteroid Redirection Test (DART) coming along?

Johnson: It's about two-thirds of the way through its integration and test now at the Applied Physics Laboratory [APL, at Johns Hopkins University in Maryland]. It is beginning to look like a real spacecraft. But there certainly have been challenges with COVID-19 and delivery by suppliers of all the parts. One of the remaining big pieces still to be delivered is the rollout solar arrays. But the integration schedule has been rearranged. Things are looking positive all the way through the testing that's going on. We're in pretty good shape to get DART shipped out to Vandenberg [Air Force Base in California] to meet the end-of-July launch. 

Space.com: Any update on the Italian Space Agency's Light Italian Cubesat for Imaging of Asteroid, the LICIACube built to witness DART's impact?

Johnson: They've had their challenges too, maybe even more so. We're hoping they will be able to stay on schedule. LICIACube could be integrated at APL, or it could also be integrated out at Vandenberg if they need to.

Space.com: As NASA's first planetary defense mission, what do you hope to learn from DART?

Johnson: It will confirm for us what the viability of the kinetic impactor technique is for diverting an asteroid's orbit and determine that it remains a viable option, at least for smaller-sized asteroids, which are the most frequent impact hazard.

Space.com: You have been engaged in a series of "table top" exercises involving the Federal Emergency Management Agency (FEMA) and other organizations about the nature, risk and what to do given an Earth encounter with an asteroid or comet impact. What's their value to your work?

Johnson: There will definitely be more coming, and possibly next year. We do introduce different scenarios, like how much time before impact do you have? Or what's the size of the object? To date, the exercises have been done with a relatively small community. I think in a future exercise, our main objective is to have a broader community of the NEO Impact Threat Emergency Protocols Working Group take part, representation from a number of other agencies that have not been involved in previous exercises. That working group was formed in early 2019 to work on Goal 5 actions in the National NEO Strategy and Action Plan.

Space.com: The JPL Center for NEO Studies is NASA's center for computing asteroid and comet orbits and their odds of Earth impact. Fireball and bolide data is included on their website, some of which is gleaned from classified military satellites. How is that data exchange between NASA and the military going?

Johnson: The pathways and the capabilities are more straightforward than it used to be. We are still working on making it faster, more automated. Through this last year some of it was somewhat manual, with data delayed longer than we would like it to be. If you check out the website, you'll see a steady addition of events into our database.

Space.com: You would want to obtain that data far sooner?

Johnson: Within hours of the event, if not quicker. 

Space.com: Asteroid samples brought back to Earth — be they from Japan's Hayabusa2 spacecraft and NASA's OSIRIS-REx — how valuable are they to your planetary defense office?

Johnson: They certainly do help us understand the nature and composition of these objects. Getting these spacecraft out there to observe them up close is part of a step-by-step approach, from remote sensing of them … and then collecting a sample for lab analysis here on Earth. It confirms what we think we know about an asteroid's composition. 

That's of course of great interest to the scientific community. But it's also of value in understanding how mitigation techniques might be more effective. For remote sensing of these objects, you are never sure whether the lines and squiggles are being interpreted correctly. When you get up close, you can confirm a number of things. So it's kind of a bootstrap approach.

• Related: The greatest asteroid encounters of all time!

Space.com: Any  new words on your proposed NASA Near Earth Object Surveyor spacecraft, a space-based infrared telescope capable of detecting asteroids close to Earth?

Johnson: From a technical standpoint, everybody agrees that this project is ready to move on into phase B, a preliminary design. The uncertainty right now is what the future budget is going to be. Our planetary defense program does not have adequate budget out through the number of years it will take to develop NEO Surveyor as yet.

Space.com: Looking back and eyeing the future, how do you appraise NASA's planetary defense program? 

Johnson: The program at NASA continues. Using ground-based capabilities in 2020, it looks like the number of found NEOs is going to hit 2,800 [for the year], a record number for us. Most of those are quite small, much smaller than the 140-meter threshold that we're working toward. 

The level of which we're finding the 140-meter and larger asteroids remains pretty stable, at about 500 a year. Our projection of the number of these objects out there is about 25,000, and we've only found a little over one-third of those so far, maybe 38% or so. Our models tell us we've got about 15,000 more to find. At 500 a year, you do the math, that's 30 years that we have to get through with these kind of operations today. We can do it quicker. We know we have the technology to do it faster, and that is what NEO Surveyor is all about.

• Leonard David is author of the book "Moon Rush: The New Space Race," which was published by National Geographic in May 2019. A longtime writer for Space.com, David has been reporting on the space industry for more than five decades. Follow us on Twitter @Spacedotcom or on Facebook. This version of the story published on Space.com.

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By Meghan Bartels 

So far, life in Earth's atmosphere seems to be strictly microbial and a temporary affair, intimately connected to life on Earth's surface rather than an independent ecosystem. Tiny, hardy organisms are swept up from the thin transition where Earth's atmosphere meets the planet and carried into the lower layers of the atmosphere on an epic detour.

"Based on what we know, the things are just moving through the atmosphere," Kevin Dillon, a Ph.D. candidate in microbiology at Rutgers University, said during the panel. "Microbes travel and use the atmosphere almost like a highway, and specifically can hitch a ride in clouds."

Microbes end up in two layers of the atmosphere. In the lower troposphere, microbes mostly have to contend with the risk of drying out, Diana Gentry, a research scientist at Ames, said during the panel. Hence the appeal of clouds.

"If you are picked up and suspended in the atmosphere, you're in danger of losing all of your water pretty quickly," Gentry said. "So clouds in the lower level are great — they're like these mobile water hotspots that can help keep you wet as you're picked up and transported around." In the troposphere, some microbes may survive pretty normally, even.

Meanwhile, life one level up, in the harsher stratosphere needs to contend with conditions that are still drier and even acidic. Here, microbes typically at least need to hunker down into a dormant state they can slip out of after returning to the surface. And of course, some die, and some are dead before they are swept up into the atmosphere.

So far, even in the best situation, atmospheric microbes don't seem to be doing much more intriguing than simply surviving, however. "We are really just beginning to understand the dynamics of how microorganisms from Earth's surface get swept up into the atmosphere, how long they stay aloft and whether or not they're doing anything meaningful in terms of activity or growth and reproduction aloft — we still don't know," Smith said. "We have a lot more work to do in Earth's atmosphere."

But just as the discovery of hydrothermal vent communities at hot seams in the ocean floor prompted astrobiological dreams of life deep inside the hidden oceans of icy moons, so scientists now wonder whether the strange extremity of atmospheric life on Earth could be a template for determining whether anything is alive elsewhere in this chain of rocky worlds we call the solar system.

Life in the solar system

Of course, for as many uncertainties as there are when it comes to life in Earth's atmosphere, they only multiply in atmospheres beyond Earth's.

One key constraint is that while we know full well Earth's surface is a paradise from which microbes can take their grand adventure, other planetary surfaces in the solar system are either certainly or likely more hostile to life as we know it, although they may well have been plenty habitable in the distant past. The appeal of someplace like Venus, for example, as a destination in the search for life is in its atmosphere, where some scientists have argued that liquid droplets about 30 to 37 miles (48 to 60 kilometers) up could act as a haven in the acidic, hot environment for which Venus is famous.

That harshness means that on worlds like Venus, life would need to remain in the atmosphere permanently, rather than visiting as it does on Earth. And that permanence means those holes scientists have about whether microbes can, say, reproduce while aloft, would need filling.

And gravity would consistently steal some hypothetical microbes out of the one cozy layer, Gentry noted. "A challenge to life that is unique to life in the atmosphere is that because you're floating, you're constantly losing some of your life that is up there, just to gravitational settling over time," she said. "In order for life to be able to persist long-term in an atmosphere, it has to be able to reproduce fast enough to make up for those losses."

Then there's that water issue. Earth's clouds are special: They are the only modern atmospheric clouds in the solar system built primarily of water vapor, making them uniquely promising for life human scientists are most attuned to recognize. Venus' clouds? Sulfuric acid. Mars has some carbon dioxide wisps. Neptune's moon Triton boasts nitrogen clouds. All of them are intriguing, but no water is a real hurdle.

"One of the major themes in astrobiology tends to be 'follow the water' because, for Earth-like life as we know it, water is a requirement," Gentry said. "Because those are not water-based clouds, they're not interesting for the same reason that water-based clouds are interesting."

And beyond

Just as Earth serves as a template for considering other solar system worlds, our neighborhood offers archetypes to consider for worlds beyond our star — with another step down in how much we know about them, of course. Where Earth is our daily backdrop and the planets are destinations for sophisticated spacecraft, exoplanets are mostly blemishes silhouetted against their stars in astronomical observations.

And it turns out, spotting atmospheric life is tricky, even here on Earth. "Every time we fly through clouds and make cloud water collections, we have this really strong signal of Earth life. And yet, we can't measure it remotely," Smith said. "We know life is in those clouds, but we don't have any instruments that are sensitive enough to detect that without actually collecting the cloud water."

So don't expect scientists to make any announcements about atmospheric life on other worlds any time soon.

"It is extraordinarily difficult to prove or to see whether an exoplanet is a living world," Noam Izenberg, a planetary scientist at Johns Hopkins University Applied Physics Laboratory in Maryland, said.

But don't stop wondering about it either, he said.

"If there's a chance for life on Venus, then yes, there's probably chances for life on Venus-like worlds elsewhere," Izenberg said. "If there's life on Earth, yes, there's probably a chance for life on Earth-like worlds elsewhere."

• Email Meghan Bartels at mbartels@space.com or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.

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