Inside Science

Tiny living machines called xenobots can create copies of themselves

Publish: 04:59 PM, 07 Dec, 2021


Tiny “living machines” made of frog cells can replicate themselves, making copies that can then go on to do the same. This newly described form of renewal offers insights into how to design biological machines that are self-perpetuating.

“This is an incredibly exciting breakthrough,” for the field of biologically based robotics, says Kirstin Petersen, an electrical and computer engineer at Cornell University who studies groups of robots. Robots that can copy themselves are an important step toward systems that don’t need humans to operate, she says.

Earlier this year, researchers described the behaviors of the lab-made living robots, called xenobots (SN: 3/31/21). Plucked out of frogs’ growing bodies, small clumps of skin stem cells from frog embryos knitted themselves into small spheres and began to move. Cellular extensions called cilia served as motors that powered the xenobots as they cruised around their lab dishes.

That cruising can have a bigger purpose, the researchers now report in the Dec. 7 Proceedings of the National Academy of Sciences. As the xenobots bumble about, they can gather loose frog cells into spheres, which then coalesce into xenobots themselves.

This type of movement-created reproduction, called kinematic self-replication by the researchers, appears to be new for living cells. Usually, reproducing organisms contribute some parental material to their offspring, says study coauthor Douglas Blackiston of Tufts University in Medford, Mass., and Harvard University. Sexual reproduction, for instance, requires parental sperm and egg cells to get started. Other types of reproduction involve cells splitting or budding off from a parent.

“Here, this is different,” Blackiston says. These xenobots are “finding loose parts, sort of like robotics parts in the environment, and cobbling them together.” Those collections then grow into “a second generation of xenobots that can move around like their parents,” Blackiston says.

Left to their own devices, spheroid xenobots could generally create only one more generation before dying out, the researchers found. But with the help of an artificial intelligence program that predicted an optimal shape for the original xenobots, the replication could be pushed to four generations.

The AI program predicted that a C shape, much like an openmouthed Pac-Man, would be a more efficient progenitor. Sure enough, when improved xenobots were let loose in a dish, they began scooping up loose cells into their gaping “mouths,” forming more sphere-shaped bots. A mobile offspring took shape once about 50 cells had glommed together in a parent’s opening, Blackiston says. A full-bodied xenobot consists of about 4,000 to 6,000 frog cells.

Xenobots’ tiny size is an advantage, Petersen says. “The fact that they were able to do this at such a small scale just makes it even better, because you can start to imagine biomedical application areas,” she says. Minuscule xenobots might be able to sculpt tissues for implantation, for instance, or go inside bodies to deliver therapeutics to specific spots.

Beyond the possible jobs for the xenobots, the research advances an important science, one that has existential importance for humans, says study coauthor Michael Levin, a developmental biologist at Tufts. That is, “the science of trying to anticipate and control the consequences of complex systems,” he says.

“Originally, no one would have predicted any of this,” Levin says. “These things are routinely doing things that surprise us.” With xenobots, researchers can push the limits of the unexpected. “This is about a safe way to explore and advance the science of being less surprised by things,” Levin says.


Inside Science

NASA, SpaceX study boosting Hubble to extend its lifespan

Publish: 09:47 AM, 02 Oct, 2022


NASA and SpaceX have agreed to study the feasibility of awarding Elon Musk's company a contract to boost the Hubble Space Telescope to a higher orbit, with a goal of extending its lifespan, the US space agency said recently.

The renowned observatory has been operating since 1990 about 335 miles (540 kilometers) above Earth, in an orbit that slowly decays over time.

Hubble has no on-board propulsion to counter the small but still present atmospheric drag in this region of space, and its altitude has previously been restored during Space Shuttle missions.

The proposed new effort would involve a SpaceX Dragon capsule.

"A few months ago, SpaceX approached NASA with the idea for a study whether a commercial crew could help reboost our Hubble spacecraft," NASA's chief scientist Thomas Zurbuchen told reporters, adding the agency had agreed to the study at no cost to itself.

He stressed there are no concrete plans at present to conduct or fund such a mission until the technical challenges are better understood.

One of the main obstacles would be that the Dragon spacecraft, unlike the Space Shuttles, does not have a robotic arm and would need modifications for such a mission.

SpaceX proposed the idea in partnership with the Polaris Program, a private human spaceflight venture led by payments billionaire Jared Isaacman, who last year chartered a SpaceX Crew Dragon to orbit the Earth with three other private astronauts.

"This would certainly fit within the parameters we established for the Polaris program," Isaacman said in response to a question about whether reboosting Hubble could be the goal for a future Polaris mission.

Asked by a reporter whether there might be a perception that the mission was contrived in order to give wealthy people tasks to do in space, Zurbuchen said: "I think it's only appropriate for us to look at this because of the tremendous value this research asset has for us."

Arguably among the most valuable instruments in scientific history, Hubble continues to make important discoveries, including this year detecting the farthest individual star ever seen -- Earendel, whose light took 12.9 billion years to reach us.

It is currently forecast to remain operational throughout this decade, with a 50 percent chance of de-orbiting in 2037, said Patrick Crouse, Hubble Space Telescope project manager.


NASA   SpaceX   Hubble Telescope  


Inside Science

NASA's DART spacecraft hits target asteroid in first planetary defense test

Publish: 09:57 AM, 27 Sep, 2022


NASA's DART spacecraft successfully slammed into a distant asteroid at hypersonic speed on Monday in the world's first test of a planetary defense system, designed to prevent a potential doomsday meteorite collision with Earth.

Humanity's first attempt to alter the motion of an asteroid or any celestial body played out in a NASA webcast from the mission operations center outside Washington, DC, 10 months after DART was launched.

The livestream showed images taken by DART's camera as the cube-shaped "impactor" vehicle, no bigger than a vending machine with two rectangular solar arrays, streaked into the asteroid Dimorphos, about the size of a football stadium, at 7:14 pm EDT (2314 GMT) some 6.8 million miles (11 million km) from Earth.

The $330 million mission, some seven years in development, was devised to determine if a spacecraft is capable of changing the trajectory of an asteroid through sheer kinetic force, nudging it off course just enough to keep Earth out of harm's way.

Whether the experiment succeeded beyond accomplishing its intended impact will not be known until further ground-based telescope observations of the asteroid next month. But NASA officials hailed the immediate outcome of Monday's test, saying the spacecraft achieved its purpose.

"NASA works for the benefit of humanity, so for us it's the ultimate fulfillment of our mission to do something like this - a technology demonstration that, who knows, someday could save our home," NASA Deputy Administrator Pam Melroy, a retired astronaut, said minutes after the impact.

DART, launched by a SpaceX rocket in November 2021, made most of its voyage under the guidance of NASA's flight directors, with control handed over to an autonomous on-board navigation system in the final hours of the journey.

Monday evening's bullseye impact was monitored in near real time from the mission operations center at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Cheers erupted from the control room as second-by-second images of the target asteroid, captured by DART's onboard camera, grew larger and ultimately filled the TV screen of NASA's live webcast just before the signal was lost, confirming the spacecraft had crashed into Dimorphos.

DART's celestial target was an oblong asteroid "moonlet" about 560 feet (170 meters) in diameter that orbits a parent asteroid five times larger called Didymos as part of a binary pair with the same name, the Greek word for twin.

Neither object presents any actual threat to Earth, and NASA scientists said their DART test could not create a new hazard by mistake.

Dimorphos and Didymos are both tiny compared with the cataclysmic Chicxulub asteroid that struck Earth some 66 million years ago, wiping out about three-quarters of the world's plant and animal species including the dinosaurs.

Smaller asteroids are far more common and present a greater theoretical concern in the near term, making the Didymos pair suitable test subjects for their size, according to NASA scientists and planetary defense experts. A Dimorphos-sized asteroid, while not capable of posing a planet-wide threat, could level a major city with a direct hit.

Also, the two asteroids' relative proximity to Earth and dual configuration make them ideal for the first proof-of-concept mission of DART, short for Double Asteroid Redirection Test.

Robotic suicide mission

The mission represented a rare instance in which a NASA spacecraft had to crash to succeed. DART flew directly into Dimorphos at 15,000 miles per hour (24,000 kph), creating the force scientists hope will be enough to shift its orbital track closer to the parent asteroid.

APL engineers said the spacecraft was presumably smashed to bits and left a small impact crater in the boulder-strewn surface of the asteroid.

The DART team said it expects to shorten the orbital path of Dimorphos by 10 minutes but would consider at least 73 seconds a success, proving the exercise as a viable technique to deflect an asteroid on a collision course with Earth - if one were ever discovered.

A nudge to asteroid millions of miles away years in advance could be sufficient to safely reroute it.

Earlier calculations of the starting location and orbital period of Dimorphos were made during a six-day observation period in July and will be compared with post-impact measurements made in October to determine whether the asteroid budged and by how much.

Monday's test also was observed by a camera mounted on a briefcase-sized mini-spacecraft released from DART days in advance, as well as by ground-based observatories and the Hubble and Webb space telescopes, but images from those were not immediately available.

DART is the latest of several NASA missions in recent years to explore and interact with asteroids, primordial rocky remnants from the solar system's formation more than 4.5 billion years ago.

Last year, NASA launched a probe on a voyage to the Trojan asteroid clusters orbiting near Jupiter, while the grab-and-go spacecraft OSIRIS-REx is on its way back to Earth with a sample collected in October 2020 from the asteroid Bennu.

The Dimorphos moonlet is one of the smallest astronomical objects to receive a permanent name and is one of 27,500 known near-Earth asteroids of all sizes tracked by NASA. Although none are known to pose a foreseeable hazard to humankind, NASA estimates that many more asteroids remain undetected in the near-Earth vicinity.

- Reuters

NASA   DART   Asteroid Redirection Test   Planetary Defense  


Inside Science

Chinese rocket falls to Earth; Nasa says Beijing did not share information

Publish: 09:11 AM, 31 Jul, 2022


A Chinese rocket fell back to Earth on Saturday over the Indian Ocean but Nasa said Beijing had not shared the "specific trajectory information" needed to know where possible debris might fall.

US Space Command said the Long March 5B rocket re-entered over the Indian Ocean at approximately 12:45 p.m. EDT Saturday (1645 GMT), but referred questions about "reentry's technical aspects such as potential debris dispersal impact location" to China.

"All spacefaring nations should follow established best practices and do their part to share this type of information in advance to allow reliable predictions of potential debris impact risk," Nasa Administrator Bill Nelson said. "Doing so is critical to the responsible use of space and to ensure the safety of people here on Earth."

Social media users in Malaysia posted video of what appeared to be rocket debris.

Aerospace Corp, a government funded nonprofit research center near Los Angeles, said it was reckless to allow the rocket's entire main-core stage – which weighs 22.5 tons (about 48,500 lb) – to return to Earth in an uncontrolled reentry.

Earlier this week, analysts said the rocket body would disintegrate as it plunged through the atmosphere but is large enough that numerous chunks will likely survive a fiery re-entry to rain debris over an area some 2,000 km (1,240 miles) long by about 70 km (44 miles) wide.

The Chinese Embassy in Washington did not immediately comment. China said earlier this week it would closely track the debris but said it posed little risk to anyone on the ground.

The Long March 5B blasted off July 24 to deliver a laboratory module to the new Chinese space station under construction in orbit, marking the third flight of China's most powerful rocket since its maiden launch in 2020. 

Fragments of another Chinese Long March 5B landed on the Ivory Coast in 2020, damaging several buildings in that West African nation, though no injuries were reported.

By contrast, he said, the United States and most other space-faring nations generally go to the added expense of designing their rockets to avoid large, uncontrolled re-entries - an imperative largely observed since large chunks of the Nasa space station Skylab fell from orbit in 1979 and landed in Australia.

Last year, Nasa and others accused China of being opaque after the Beijing government kept silent about the estimated debris trajectory or the reentry window of its last Long March rocket flight in May 2021. 

Debris from that flight ended up landing harmlessly in the Indian Ocean.

- Reuters

Chinese rocket   NASA  


Inside Science

Meteor impact left 'uncorrectable' damage to the Webb telescope's mirror

Publish: 12:02 PM, 21 Jul, 2022


Since launching on Dec. 25, 2021, NASA's James Webb Space Telescope (JWST) has been pelted by at least 19 tiny space rocks — including one large one that left noticeable damage on one of the telescope's 18 gold-plated mirrors.

In a sprawling new status report posted to the pre-print database (opens in new tab), NASA researchers have shared the first images showing the extent of that damage. Seen on the C3 mirror in the lower right-hand corner of the image, the impact site appears as a single bright white dent besmirching the golden mirror's surface.

The impact — which likely occurred between May 23 and May 25 this year — left "uncorrectable" damage to a tiny portion of that mirror, the report says. However, this little dent doesn't seem to have inhibited the telescope's performance at all. In fact, the JWST's performance is exceeding expectations "almost all across the board." (Good news for fans of stunning space images.)

Tiny rocks known as micrometeoroids are an all-too-familiar threat to spacecraft in near-Earth orbit. The U.S. Space Surveillance Network keeps track of more than 23,000 pieces of orbital debris measuring larger than the size of a softball — however, the millions of nearby space chunks that are smaller than that are almost impossible to monitor.

Instead, NASA and other space agencies plan for unavoidable impacts.

"Inevitably, any spacecraft will encounter micrometeoroids," the new report says. So far, six micrometeoroids have left noticeable "deformities" on the JWST's mirrors, amounting to about one noticeable impact per month since the telescope launched.

That's all within the realm of the expected. When building the JWST, engineers intentionally hit mirror samples with micrometeoroid-sized objects to test how such impacts would affect the telescope's performance.

What was unexpected, however, was the size of the larger impactor that dented the C3 mirror. This space rock was seemingly larger than the team had prepared for, and researchers are now trying to assess the impact that further strikes like this could have on the JWST.

The new status report, which has not yet been peer-reviewed, was authored by more than 200 scientists working at NASA, the European Space Agency (a collaborator in the JWST's construction and launch, along with NASA and the Canadian Space Agency) and other science institutions around the world. Despite the unexpected impact to the C3 mirror, the researchers found that the telescope is working flawlessly after the 6-month commissioning process, and has a bright future of discovery ahead of it.

"JWST was envisioned 'to enable fundamental breakthroughs in our understanding of the formation and evolution of galaxies, stars, and planetary systems,'" the report says. "We now know with certainty that it will."

JWST   James Webb Space Telescope   Meteor impact  


Inside Science

Webb space telescope opens door to discoveries still unimagined

Publish: 11:42 AM, 14 Jul, 2022


The powerful James Webb Space Telescope's inaugural batch of images has opened a new chapter of cosmic exploration, but astronomers say the observatory's most consequential discoveries may well be those they have yet to even imagine.

Distant colliding galaxies, gas-giant exoplanets and dying star systems were the first celestial subjects captured by the multibillion-dollar observatory, putting its wide range of infrared-imaging capabilities on colorful display and proving the telescope works as designed.

Webb's gallery of early photos and spectrographic data, which astronomers likened to the results of mere "target practice" as they readied the telescope for operational science, also previewed several planned areas of inquiry ahead.

The competitively-selected agenda of research includes exploring the evolution of early galaxies, the life cycle of stars, the search for habitable planets orbiting distant suns, and the composition of moons in our own outer solar system.

But the most revolutionary findings by Webb, 100 times more sensitive than its 30-year-old predecessor, the still-operational Hubble Space Telescope, may turn out to be accidental discoveries or answers to questions astronomers have yet to ask.

"Who knows what's coming for JWST. But I'm sure we're going to have a lot of surprises," René Doyon, principal investigator for one of Webb's instruments, the Near-Infrared Imager and Slitless Spectrograph, said Tuesday at NASA's Goddard Space Flight Center in Maryland, where the agency unveiled the observatory's first full-color images.

With Webb open for business seven months after its launch in December, astronomers are preparing for "something that's out there that we never guessed would be there at all," said John Mather, a Nobel Prize-winning senior astrophysicist at NASA whose work during the 1990s helped cement cosmology's 'Big Bang' theory.


Mather and other scientists pointed to dark matter, an invisible and little-understood but theoretically influential cosmic scaffolding, as an enigma that Webb might unlock during its mission.

Hubble, likewise, opened a whole new field of astrophysics devoted to another mysterious phenomenon, dark energy, as its observations of supernovas led to the unexpected discovery that the universe's expansion is accelerating.

Taken together, dark energy and dark matter are now estimated by scientists to account for 95% of the known universe. All the galaxies, planets, dust, gases and other visible matter in the cosmos compose just 5%.

"Those were huge surprises," Mather said of early dark matter and dark energy discoveries.

Amber Straughn, a deputy project scientist working with Webb, said: "It's hard to imagine what we might learn with this hundred-times-more-powerful instrument that we really don't know yet."

Dark matter already has figured prominently in Webb's very first "deep field" image, a composite photo of a distant galaxy cluster, SMACS 0723, that offers the most detailed glimpse to date of the early universe thanks to a magnifying effect called a gravitational lens.

The sheer combined mass of galaxies and other unseen matter in the foreground of the image warps the surrounding space enough to amplify light coming from more distant galaxies behind them, bringing into view fainter objects farther away, and thus further back in time.

At least one of the tiny specks of light "photo-bombing" the edge of the picture dates back 13.1 billion years, or nearly 95% of the way to the Big Bang, the theoretical cosmic flashpoint that put the universe in motion 13.8 billion years ago.

But because the calculated combined mass of all the visible matter in the foreground is insufficient by itself to produce the faint circular distortion seen in the image, the lensing effect is firm indirect evidence of dark matter's presence.

"It's the most powerful tool that we have, astrophysically, to do this type of lensing experiment," said Jane Rigby, a Webb operations project scientist. "We can't directly detect dark matter, but we see its impact... we can see its effects in action."

"The universe has been out there, we just had to build a telescope to see what was there," she added.

New light was also shed unexpectedly from Webb's first spectrographic analysis of an exoplanet in a distant solar system, in this case a gas giant roughly the size of Jupiter dubbed WASP-96 b.

Measuring the wavelengths from light filtered through the atmosphere of the exoplanet as it orbited its own sun clearly revealed the molecular signature of water vapor in clouds and haze, features scientists were surprised to find.

"There are discoveries in these data," Webb program scientist Eric Smith said. "We're making discoveries and we really haven't even started trying yet."

- Reuters

James Webb Telescope   Cosmos   NASA