This photo taken from the ISS above the South China Sea on Oct. 30 2021 shows a pair of unrelated bright blue blobs in Earth’s atmosphere. (Image credit: NASA Earth Obsrvatory)
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An astronaut onboard the International Space Station (ISS) has snapped a peculiar image of Earth from space that contains two bizarre blue blobs of light glimmering in our planet’s atmosphere. The dazzling pair may look otherworldly. But in reality, they are the result of two unrelated natural phenomena that just happened to occur at the same time.
The image was captured last year by an unnamed member of the Expedition 66 crew as the ISS passed over the South China Sea. The photo was released online Oct. 9 by NASA’s Earth Observatory (opens in new tab).
The first blob of light, which is visible at the bottom of the image, is a massive lightning strike somewhere in the Gulf of Thailand. Lightning strikes are typically hard to see from the ISS, as they’re usually covered by clouds. But this particular strike occurred next to a large, circular gap in the top of the clouds, which caused the lightning to illuminate the surrounding walls of the cloudy caldera-like structure, creating a striking luminous ring.
Related: Upward-shooting ‘blue jet’ lightning spotted from International Space Station
The second blue blob, which can be seen in the top right of the image, is the result of warped light from the moon. The orientation of Earth’s natural satellite in relation to the ISS means the light it reflects back from the sun passes straight through the planet’s atmosphere, which transforms it into a bright blue blob with a fuzzy halo. This effect is caused by some of the moonlight scattering off tiny particles in Earth’s atmosphere, according to Earth Observatory.
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The first blue blob was the result of a lightning strike illuminating a large bowl of uncovered cloud in the Gulf of Thailand. (Image credit: NASA Earth Obsrvatory)
The second blue blob is the result of moonlight scattering of particles in Earth’s atmospehre. (Image credit: NASA Earth Obsrvatory)
Different colors of visible light have different wavelengths, which affects their interaction with atmospheric particles. Blue light has the shortest wavelength and is therefore the most likely to scatter, which caused the moon to turn blue in this image. The same effect also explains why the sky appears blue during the daytime: because blue wavelengths of sunlight scatter the most and become more visible to the human eye, according to NASA (opens in new tab).
Also visible in the photo is a glowing web of artificial lights coming from Thailand. The other prominent sources of light pollution in the image are emitted from Vietnam and Hainan Island, the southernmost region of China, though these light sources are largely obscured by clouds. The orange halo parallel to the curvature of the Earth is the edge of the atmosphere, which is commonly known as “Earth’s limb” when viewed from space, according to Earth Observatory.
Scientists who were surveying a catalog of gas clouds spotted something strange: five “blue blobs” composed of young blue stars in the Virgo galaxy cluster.
Unusually, these stars were completely isolated from their parent galaxies, and their stars were arranged in an irregular pattern. Based on those details, the researchers think they’ve discovered a new type of stellar system — a collection of gravitationally bound stars that’s not quite a galaxy but not a known type of star cluster, either.
Even more mysteriously, the blobs were determined to have little atomic hydrogen gas, which is a crucial ingredient in star formation. So how did the young stars form, especially given their distance from the closest potential parent galaxies?
Related:Mysterious blobs around M-dwarf stars may be bad news for alien life
The research team — led by Michael Jones, a postdoctoral fellow at the University of Arizona Steward Observatory — noted the presence of heavy metals in the blobs. “This tells us that these stellar systems formed from gas that was stripped from a big galaxy, because how metals are built up is by many repeated episodes of star formation, and you only really get that in a big galaxy,” Jones said in a statement.
There are only two main ways gas is stripped from a galaxy: tidal stripping, in which the gravitational attraction between passing galaxies pulls gas away from them, and ram pressure stripping, which is “[w]hen a galaxy belly flops into a cluster that is full of hot gas, then its gas gets forced out behind it,” Jones said. “That’s the mechanism that we think we’re seeing here to create these objects.”
The astronomers suspect that, over time, the stars in the blobs will split into smaller stellar clusters and spread out.
The team’s findings were presented June 15 at the 240th American Astronomical Society meeting in Pasadena, California.
Follow Stefanie Waldek on Twitter @StefanieWaldek.Follow uson Twitter @Spacedotcom and on Facebook.
UArizona astronomers have identified a new class of star system. The collection of mostly young blue stars are seen here using the Hubble Space Telescope Advanced Camera for Surveys. Credit: Michael Jones
University of Arizona astronomers have identified five examples of a new class of stellar system. They’re not quite galaxies and only exist in isolation.
The new stellar systems contain only young, blue stars, which are distributed in an irregular pattern and seem to exist in surprising isolation from any potential parent galaxy.
The stellar systems—which astronomers say appear through a telescope as “blue blobs” and are about the size of tiny dwarf galaxies—are located within the relatively nearby Virgo galaxy cluster. The five systems are separated from any potential parent galaxies by more than 300,000 light years in some cases, making it challenging to identify their origins.
The astronomers found the new systems after another research group, led by the Netherlands Institute for Radio Astronomy’s Elizabeth Adams, compiled a catalog of nearby gas clouds, providing a list of potential sites of new galaxies. Once that catalog was published, several research groups, including one led by UArizona associate astronomy professor David Sand, started looking for stars that could be associated with those gas clouds.
The gas clouds were thought to be associated with our own galaxy, and most of them probably are, but when the first collection of stars, called SECCO1, was discovered, astronomers realized that it was not near the Milky Way at all, but rather in the Virgo cluster, which is much farther away but still very nearby in the scale of the universe.
SECCO1 was one of the very unusual “blue blobs,” said Michael Jones, a postdoctoral fellow in the UArizona Steward Observatory and lead author of a study that describes the new stellar systems. Jones presented the findings, which Sand co-authored, during the 240th American Astronomical Society meeting in Pasadena, California, Wednesday.
“It’s a lesson in the unexpected,” Jones said. “When you’re looking for things, you’re not necessarily going to find the thing you’re looking for, but you might find something else very interesting.”
The team obtained their observations from the Hubble Space Telescope, the Very Large Array telescope in New Mexico and the Very Large Telescope in Chile. Study co-author Michele Bellazzini, with the Istituto Nazionale di Astrofisica in Italy, led the analysis of the data from Very Large Telescope and has submitted a companion paper focusing on that data.
Together, the team learned that most of the stars in each system are very blue and very young and that they contain very little atomic hydrogen gas. This is significant because star formation begins with atomic hydrogen gas, which eventually evolves into dense clouds of molecular hydrogen gas before forming into stars.
“We observed that most of the systems lack atomic gas, but that doesn’t mean there isn’t molecular gas,” Jones said. “In fact, there must be some molecular gas because they are still forming stars. The existence of mostly young stars and little gas signals that these systems must have lost their gas recently.”
The combination of blue stars and lack of gas was unexpected, as was a lack of older stars in the systems. Most galaxies have older stars, which astronomers refer to as being “red and dead.”
“Stars that are born red are lower mass and therefore live longer than blue stars, which burn fast and die young, so old red stars are usually the last ones left living,” Jones said. “And they’re dead because they don’t have any more gas with which to form new stars. These blue stars are like an oasis in the desert, basically.”
The fact that the new stellar systems are abundant in metals hints at how they might have formed.
“To astronomers, metals are any element heavier than helium,” Jones said. “This tells us that these stellar systems formed from gas that was stripped from a big galaxy, because how metals are built up is by many repeated episodes of star formation, and you only really get that in a big galaxy.”
There are two main ways gas can be stripped from a galaxy. The first is tidal stripping, which occurs when two big galaxies pass by each other and gravitationally tear away gas and stars.
The other is what’s known as ram pressure stripping.
“This is like if you belly flop into a swimming pool,” Jones said. “When a galaxy belly flops into a cluster that is full of hot gas, then its gas gets forced out behind it. That’s the mechanism that we think we’re seeing here to create these objects.”
The team prefers the ram pressure stripping explanation because in order for the blue blobs to have become as isolated as they are, they must have been moving very quickly, and the speed of tidal stripping is low compared to ram pressure stripping.
Astronomers expect that one day these systems will eventually split off into individual clusters of stars and spread out across the larger galaxy cluster.
What researchers have learned feeds into the larger “story of recycling of gas and stars in the universe,” Sand said. “We think that this belly flopping process changes a lot of spiral galaxies into elliptical galaxies on some level, so learning more about the general process teaches us more about galaxy formation.”
Hubble focuses on large lenticular galaxy 1023
More information:
Michael G. Jones et al, Young, blue, and isolated stellar systems in the Virgo Cluster. II. A new class of stellar system. arXiv:2205.01695v1 [astro-ph.GA], arxiv.org/abs/2205.01695
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Deep in the Earth beneath us lie two blobs the size of continents. One is under Africa, the other under the Pacific Ocean.
The blobs have their roots 2,900 km (1,800 miles) below the surface, almost halfway to the centre of the Earth. They are thought to be the birthplace of rising columns of hot rock called “deep mantle plumes” that reach Earth’s surface.
When these plumes first reach the surface, giant volcanic eruptions occur – the kind that contributed to the extinction of the dinosaurs 65.5 million years ago. The blobs may also control the eruption of a kind of rock called kimberlite, which brings diamonds from depths 120-150 km (and in some cases up to around 800 km) to Earth’s surface.
Scientists have known the blobs existed for a long time, but how they have behaved over Earth’s history has been an open question. In new research, we modeled a billion years of geological history and discovered the blobs gather together and break apart much like continents and supercontinents.
(Ömer Bodur)
Above: Earth’s blobs as imaged from seismic data. The African blob is at the top and the Pacific blob at the bottom.
A model for Earth blob evolution
The blobs are in the mantle, the thick layer of hot rock between Earth’s crust and its core. The mantle is solid but slowly flows over long timescales. We know the blobs are there because they slow down waves caused by earthquakes, which suggests the blobs are hotter than their surroundings.
Scientists generally agree the blobs are linked to the movement of tectonic plates at Earth’s surface. However, how the blobs have changed over the course of Earth’s history has puzzled them.
One school of thought has been that the present blobs have acted as anchors, locked in place for hundreds of millions of years while other rock moves around them. However, we know tectonic plates and mantle plumes move over time, and research suggests the shape of the blobs is changing.
Our new research shows Earth’s blobs have changed shape and location far more than previously thought. In fact, over history they have assembled and broken up in the same way that continents and supercontinents have at Earth’s surface.
We used Australia’s National Computational Infrastructure to run advanced computer simulations of how Earth’s mantle has flowed over a billion years.
These models are based on reconstructing the movements of tectonic plates. When plates push into one another, the ocean floor is pushed down between them in a process known as subduction.
The cold rock from the ocean floor sinks deeper and deeper into the mantle, and once it reaches a depth of about 2,000 km it pushes the hot blobs aside.
Above: The past 200 million years of Earth’s interior. Hot structures are in yellow to red (darker is shallower) and cold structures in blue (darker is deeper).
We found that just like continents, the blobs can assemble – forming “superblobs” as in the current configuration – and break up over time.
A key aspect of our models is that although the blobs change position and shape over time, they still fit the pattern of volcanic and kimberlite eruptions recorded at Earth’s surface. This pattern was previously a key argument for the blobs as unmoving “anchors”.
Strikingly, our models reveal the African blob assembled as recently as 60 million years ago – in stark contrast to previous suggestions the blob could have existed in roughly its present form for nearly ten times as long.
Remaining questions about the blobs
How did the blobs originate? What exactly are they made of? We still don’t know.
The blobs may be denser than the surrounding mantle, and as such they could consist of material separated out from the rest of the mantle early in Earth’s history. This could explain why the mineral composition of the Earth is different from that expected from models based on the composition of meteorites.
Alternatively, the density of the blobs could be explained by the accumulation of dense oceanic material from slabs of rock pushed down by tectonic plate movement.
Regardless of this debate, our work shows sinking slabs are more likely to transport fragments of continents to the African blob than to the Pacific blob.
Interestingly, this result is consistent with recent work suggesting the source of mantle plumes rising from the African blob contains continental material, whereas plumes rising from the Pacific blob do not.
Tracking the blobs to find minerals and diamonds
While our work addresses fundamental questions about the evolution of our planet, it also has practical applications.
Our models provide a framework to more accurately target the location of minerals associated with mantle upwelling. This includes diamonds brought up to the surface by kimberlites that seem to be associated with the blobs.
Magmatic sulfide deposits, which are the world’s primary reserve of nickel, are also associated with mantle plumes. By helping target minerals such as nickel (an essential ingredient of lithium-ion batteries and other renewable energy technologies) our models can contribute to the transition to a low-emission economy.
Nicolas Flament, Senior Lecturer, University of Wollongong; Andrew Merdith, Research fellow, University of Leeds; Ömer F. Bodur, Postdoctoral research fellow, University of Wollongong, and Simon Williams, Research Fellow, Northwest University, Xi’an.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
For years scientists have been scratching their heads over two unexplained massive blobs of rock under Earth’s surface.
Many theories have been thrown around since their discovery in the 1980s, including claims that they could be huge fragments of an alien world.
The blobs of rock under Earth’s crust are each the size of a continent and 100 times taller than Mount Everest.
One sits under Africa, while the other can be found under the Pacific Ocean.
In pursuit of answers, a pair of experts have made some interesting new discoveries about the two gigantic masses.
As suspected, it turns out, the blob under Africa is a lot higher.
In fact, it’s twice the height of the one on the opposite side of the world, measuring in about 620 miles taller.
And that’s not all.
Crucially, scientists have found that the African blob of rock is also less dense and less stable.
It’s not clear why things are this way but it could be a reason for the continent having significantly more supervolcano eruptions over hundreds of millions of years, compared to its counterpart on the other side.
A 3D model of the blobs beneath Earth’s mantle in Africa. Mingming Li/ASU
“This instability can have a lot of implications for the surface tectonics, and also earthquakes and supervolcanic eruptions,” said Qian Yuan, from Arizona State University.
These thermo-chemical materials – officially known as large low-shear-velocity provinces (LLSVPs) – were studied by looking at data from seismic waves and running hundreds of simulations.
While we now know they both have different compositions, we’re yet to work out how this affects the surrounding mantle, which is found between the planet’s core and the crust.
And most importantly, we’re no closer to figuring out where these mysterious blobs came from.
“Our combination of the analysis of seismic results and the geodynamic modeling provides new insights on the nature of the Earth’s largest structures in the deep interior and their interaction with the surrounding mantle,” Yuan added.
“This work has far-reaching implications for scientists trying to understand the present-day status and the evolution of the deep mantle structure, and the nature of mantle convection.”
And so, the investigation continues.
The research was published in the Nature Geoscience journal.
This article originally appeared on The Sun and was reproduced here with permission.
A 3D view of the blob in Earth’s mantle beneath Africa, shown by the red-yellow-orange colors. The cyan color represents the core-mantle boundary, blue signifies the surface, and the transparent gray signifies continents. Credit: Mingming Li/ASU
Earth is layered like an onion, with a thin outer crust, a thick viscous mantle, a fluid outer core, and a solid inner core. Within the mantle, there are two massive blob-like structures, roughly on opposite sides of the planet. The blobs, more formally referred to as Large Low-Shear-Velocity Provinces (LLSVPs), are each the size of a continent and 100 times taller than Mt. Everest. One is under the African continent, while the other is under the Pacific Ocean.
Using instruments that measure seismic waves, scientists know that these two blobs have complicated shapes and structures, but despite their prominent features, little is known about why the blobs exist or what led to their odd shapes.
Arizona State University scientists Qian Yuan and Mingming Li of the School of Earth and Space Exploration set out to learn more about these two blobs using geodynamic modeling and analyses of published seismic studies. Through their research, they were able to determine the maximum heights that the blobs reach and how the volume and density of the blobs, as well as the surrounding viscosity in the mantle, might control their height. Their research was recently published in
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A 3D view of the blob in Earth’s mantle beneath Africa, shown in red, yellow and orange. The cyan represents the core-mantle boundary, blue signifies the surface and transparent gray indicates continents. (Image credit: Mingming Li/ASU)
Deep within Earth’s mantle, there are two giant blobs. One sits under Africa, while the other is almost precisely opposite the first, under the Pacific Ocean. But these two blobs are not evenly matched.
New research finds that the blob under Africa extends far closer to the surface — and is more unstable — than the blob under the Pacific. This difference could ultimately help to explain why the crust under Africa has been lifted upward and why the continent has seen so many large supervolcano eruptions over hundreds of millions of years.
“This instability can have a lot of implications for the surface tectonics, and also earthquakes and supervolcanic eruptions,” said Qian Yuan, a graduate associate in geology at Arizona State University (ASU) who led the research.
A pair of blobs
The mantle blobs are properly known as “large low-shear-wave-velocity provinces,” or LLSVPs. This means that when seismic waves generated by earthquakes travel through these deep-mantle zones, the waves slow down. This deceleration indicates that there’s something different about the mantle at this spot, such as density or temperature — or both.
Scientists aren’t sure why the mantle blobs exist. There are two popular hypotheses, Yuan told Live Science. One is that they’re made up of accumulations of crust that have subducted from Earth‘s surface to deep inside the mantle. Another is that they’re the remnants of an ocean of magma that may have existed in the lower mantle during Earth’s early history. As this magma ocean cooled and crystallized, it may have left behind areas that were denser than the rest of the mantle.
Prior studies had hinted that these two blobs may not have been created equal, Yuan said, but none of this research had used global data sets that could easily compare the two. He and his adviser, ASU geodynamics assistant professor Mingming Li, examined 17 global seismic-wave data sets to determine the height of each blob.
They found that the African blob extends about 620 miles (1,000 kilometers) higher than the Pacific blob. That’s a difference of roughly 113 Mount Everests. In total, the Pacific blob extends 435 to 500 miles (700 to 800 km) upward from the boundary between the core and the mantle. The African blob extends upward about 990 to 1,100 miles (1,600 to 1,800 km).
Blobular instability
Even though the African blob is in Earth’s mantle layer (shown here), far beneath the crust, the structure’s instability may have implications for the planet’s surface. (Image credit: vectortatu/Shutterstock)
The researchers then used computer modeling to figure out which features of the blobs could explain these differences. The most important ones, they found, were the density of the blobs themselves and the viscosity of the surrounding mantle. Viscosity refers to the ease with which the mantle rocks can be deformed.
For the African blob to be so much taller than the Pacific blob, it must be far less dense, according to Yuan. “Because it’s less dense, it’s unstable,” he said.
The African blob is still far from Earth’s crust — the mantle is 1,800 miles (2,900 km) thick in total — but this deep structure’s instability may have implications for the planet’s surface. LLSVPs may be a source of hot plumes of mantle material that rise upward. These plumes, in turn, might cause supervolcano eruptions, tectonic upheaval and possibly even continental breakup, Yuan said.
The African blob “is very close to the surface, so there is a possibility that a large mantle plume may rise from the African blob and may lead to more surface rising and earthquakes and supervolcano eruptions,” Yuan said.
These processes occur over many millions of years and have been ongoing in Africa. There does seem to be a connection between the African blob and major eruptions, Yuan said. A 2010 paper published in the journal Nature found that in the past 320 million years, 80% of kimberlites, or huge eruptions of mantle rock that bring diamonds to the surface, have occurred right over the boundary of the African blob.
Yuan and Li published their findings March 10 in the journal Nature Geoscience. They are now working on research into the origins of the blobs. Though those findings have not yet been published in a peer-reviewed journal, the researchers presented the results at the 52nd Lunar and Planetary Science Conference in March 2021; that research suggested that the blobs might be remnants of the planet-size object that slammed into Earth some 4.5 billion years ago, forming the moon.
Earth’s interior is not a uniform stack of layers. Deep in its thick middle layer lie two colossal blobs of thermo-chemical material.
To this day, scientists still don’t know where both of these colossal structures came from or why they have such different heights, but a new set of geodynamic models has landed on a possible answer to the latter mystery.
These hidden reservoirs are located on opposite sides of the world, and judging from the deep propagation of seismic waves, the blob under the African continent is more than twice as high as the one under the Pacific ocean.
After running hundreds of simulations, the authors of the new study think the blob under the African continent is less dense and less stable than its Pacific counterpart, and that’s why it’s so much taller.
“Our calculations found that the initial volume of the blobs does not affect their height,” explains geologist Qian Yuan from Arizona State University.
“The height of the blobs is mostly controlled by how dense they are and the viscosity of the surrounding mantle.”
3D view of the blob in Earth’s mantle beneath Africa. (Mingming Li/ASU)
One of the principal layers inside Earth is the hot and slightly goopy mess known as the mantle, a layer of silicate rock that sits between our planet’s core and its crust. While the mantle is mostly solid, it behaves sort of like tar on longer timescales.
Over time, columns of hot magma rock gradually rise through the mantle and are thought to contribute to volcanic activity on the planet’s surface.
Understanding what’s going on in the mantle is thus an important endeavor in geology.
The Pacific and African blobs were first discovered in the 1980s. In scientific terms, these ‘superplumes’ are known as large low-shear-velocity provinces (LLSVPs).
Compared to the Pacific LLSVP, the current study found the African LLSVP stretches about 1,000 kilometers higher (621 miles), which supports previous estimates.
This vast height difference suggests both of these blobs have different compositions. How this impacts the surrounding mantle, however, is unclear.
Perhaps the less stable nature of the African pile, for instance, can explain why there is such intense volcanism in some regions of the continent. It could also impact the movement of tectonic plates, which float on the mantle.
Other seismic models have found the African LLSVP stretches up to 1,500 kilometers above the outer core, whereas the Pacific LLSVP reaches 800 kilometers high at max.
In lab experiments that seek to replicate Earth’s interior, both the African and Pacific piles appear to oscillate up and down through the mantle.
The authors of the current study say this supports their interpretation that the African LLSVP is probably unstable, and the same could go for the Pacific LLSVP, although their models didn’t show this.
The different compositions of the Pacific and African LLSVPs could also be explained by their origins. Scientists still don’t know where these blobs came from, but there are two main theories.
One is that the piles are made from subducted tectonic plates, which slip into the mantle, are super-heated and gradually fall downwards, contributing to the blob.
Another theory is that the blobs are remnants of the ancient collision between Earth and the protoplanet Thea, which gave us our Moon.
The theories are not mutually exclusive, either. For instance, perhaps Thea contributed more to one blob; this could be part of the reason why they look so different today.
“Our combination of the analysis of seismic results and the geodynamic modeling provides new insights on the nature of the Earth’s largest structures in the deep interior and their interaction with the surrounding mantle,” says Yuan.
“This work has far-reaching implications for scientists trying to understand the present-day status and the evolution of the deep mantle structure, and the nature of mantle convection.”
As Pac-man-shaped xenobot “parents” move around their environment, they collect loose stem cells in their “mouths” that, over time, aggregate to create “offspring” xenobots that develop to look just like their creators. (Image credit: Doug Blackiston and Sam Kriegman)
Tiny groups of cells shaped like Pac-Man are the world’s first self-replicating biological robots.
The tiny bots are made from the skin cells of frogs, but they don’t reproduce by mitosis or meiosis or any of the other ways cells divide and replicate in normal circumstances. Instead, they build more of themselves from raw materials — free-floating frog skin cells — creating multiple generations of nearly identical organisms.
In action, the bots (dubbed “xenobots” by their inventors), even look like Pac-Man. They move in wild corkscrews and spirals, their open “mouths” scooping the free-floating skin cells into piles. The cells tend to adhere, or stick together, once put in contact with one another, so these piles gradually meld into new, spiraling xenobots.
Though this self-replication is a fairly delicate process, so far possible only in a carefully controlled lab dish, researchers hope it offers new promise for biologically based robots.
Related: 11 body parts grown in the lab
“The ability to make a copy of yourself is the ultimate way to make sure you keep doing whatever it is you do,” said Sam Kriegman, a computer scientist and postdoctoral scholar at the Wyss Institute at Harvard University and the Allen Discovery Center at Tufts University.
Bio-bots
Kriegman and his colleagues, including computer scientist Joshua Bongard of the University of Vermont, have been developing the xenobots for years. The bots are made from stem cells taken from frog eggs and are 0.04 inches (1 millimeter) wide or less. When put in contact with each other, the stem cells naturally form spherical blobs covered with tiny, beating cilia, or hairlike structures that can propel the blobs around.
“They’re neither a traditional robot nor a known species of animal,” Bongard said in a statement when the invention of xenobots was first announced in 2020, Live Science reported at the time. “It’s a new class of artifact: a living, programmable organism.”
Programming an organism isn’t as easy as entering commands into code, though, Kriegman told Live Science. “It’s difficult to program something that doesn’t have software,” he said.
Ultimately, control of the xenobots comes down to control of their shapes. That’s where artificial intelligence comes into play. It’s not always intuitive what a xenobot will do when you alter its shape, or how to get a desired outcome by sculpting the shape. But computer simulations can run through billions of shape and size options in days or weeks. Researchers can even vary the environment around the simulated xenobots. Promising shapes, sizes and environments can then be tested in the real world.
An artificial-intelligence-generated Pac-Man shaped parent xenobot scoops up a sphere of stem cells. (Image credit: Douglas Blackiston and Sam Kriegman)
Biological robots are promising, Kriegman said, because they can self-repair. They’re also biodegradable. Left to their own devices, the xenobots run out of energy and begin to degrade within 10 to 14 days. They don’t leave microplastics or toxic metals behind, just tiny specks of organic decay. The researchers are working on designs that might allow the xenobots to carry small amounts of material. Potential uses include delivering drugs inside the body or cleaning up toxic chemicals in the environment.
Self-replication
In their typical spherical shape, the xenobots are capable of a limited version of self-replication, the researchers found. When put in a dish full of independently floating frog stem cells, the blobs circle merrily, randomly pushing the free-floating cells into clumps, some of which stick together to form new xenobots. These tend to be smaller than their parents, however, and typically they aren’t capable of moving around enough single cells to create yet another generation.
After computer simulations suggested that a Pac-Man shape might be more effective, the researchers tested these C-shaped xenobots in a soup of stem cells. They found that the diameter of the offspring of Pac-Man xenobots was 149% larger than the offspring of spherical xenobots. Thanks to the size improvements, the baby xenobots were able to create their own offspring. Instead of just one generation of xenobot replication, the researchers found they were able to reach three or four.
The system is still quite fragile, and the process of growing the cells and making sure their growth substrate is clean and fresh is tedious, Kriegman said. And not to worry, as there’s no concern that these biological robots will replicate out of control and take over the world: “If you sneeze on the dish, you’ll ruin the experiment,” Kriegman said.
That also means the xenobots aren’t quite ready to become working robots. The researchers are still working on testing different shapes for different tasks. Their AI simulation also suggested that varying the shape of the lab dishes the xenobots replicate in might lead to better results, but that still needs to be tested in the real world.
However, there are lessons from the xenobots that could be incorporated into robotics right away, Kriegman said. One is that artificial intelligence can be used to design robots, even robots that can self-replicate. Another is that it makes sense to create robots from intelligent components. Biological organisms are smart all the way down to their component parts, he said: Organisms are made of self-organizing cells, which are made of self-organizing organelles, which are made of self-assembling proteins and molecules. Current metal-and-plastic robots don’t work in that way.
“If we could build robots out of intelligent modules, maybe we could create more robust machines,” Kriegman said. “Maybe we could create robots in the real world that could self-repair or self-replicate.”
We’ve seen how 3D-printing can revolutionize certain manufacturing processes – whether on Earth or anywhere else – but there’s a growing field of research looking at ways this can be applied to producing living, biological structures as well.
In a new study, scientists have outlined a new type of ‘living ink’ or bioink made from programmed Escherichia coli bacterial cells, which can be 3D-printed to create hydrogels in different kinds of shapes that release different types of drugs or absorb toxins, depending on how they’re engineered.
What makes this approach different from previous bioinks is how it uses genetic programming to control the mechanical properties of the ink itself – leading to better end results in the finished material and more practical uses for the ink (some existing bioinks don’t operate properly at room temperature, for example).
Examples of the printed bioink. (Joshi et al., Nature Communications, 2021)
“A tree has cells embedded within it and it goes from a seed to a tree by assimilating resources from its surroundings in order to enact these structure-building programs,” says chemical biologist Neel Joshi from Northeastern University in Massachusetts.
“What we want to do is a similar thing, but where we provide those programs in the form of DNA that we write, and genetic engineering.”
The way it works is by bioengineering the bacterial cells to create living nanofibers. The E. coli cells were combined with other substances to create the fibers, using a chemical process inspired by fibrin – a protein that plays a key part in blood clots in mammals.
These protein-based nanofibers can then be fed into a 3D-printer and manipulated into various shapes. Unlike previous bioinks, this one doesn’t use any artificial substances, and is instead entirely biological. It’s squeezed out like a toothpaste, but can then keep its form if it is kept from drying out.
So far the technique has been used to make very small objects: a circle, a square, and a cone. But now that the scientists have shown that the microbial ink can be 3D-printed in this way, it opens up more possibilities for the future.
“If you were to take that whole cone and dunk it into some glucose solution, the cells would eat that glucose and they would make more of that fiber and grow the cone into something bigger,” says Joshi.
“There is the option to leverage the fact that there are living cells there. But you can also just kill the cells and use it as an inert material.”
In experiments, the team was able to combine their bioink with other microbes to perform specific tasks: absorbing toxic chemicals, for example, or delivering an anti-cancer drug. In the future, the ink could also be engineered to self-replicate, the researchers say.
This study builds on previous work by the same team, looking at how E. coli cells could be formed into a hydrogel that self-replicates when it comes into contact with a particular tissue – opening up a new and sustainable method of manufacture that could be used on the Moon and Mars as well as here on Earth.
Although the 3D-printable bioink has only been used on a small scale so far, further down the line it could ultimately be used in everything from building self-healing structures to producing bottle caps that are able to remove dangerous chemicals from water.
“Biology is able to do similar things,” says Joshi. “Think about the difference between hair, which is flexible, and horns on a deer or a rhino or something. They’re made of similar materials, but they have very different functions. Biology has figured out how to tune those mechanical properties using a limited set of building blocks.”
The research has been published in Nature Communications.
