Topics: Astrobiology, Philosophy, SETI, Space Exploration
In my freshman seminar at Harvard last semester, I mentioned that the nearest star to the sun, Proxima Centauri, emits mostly infrared radiation and has a planet, Proxima b, in the habitable zone around it. As a challenge to the students, I asked: “Suppose there are creatures crawling on the surface of Proxima b? What would their infrared-sensitive eyes look like?” The brightest student in class responded within seconds with an image of the mantis shrimp, which possesses infrared vision. The shrimp’s eyes look like two ping-pong balls connected with cords to its head. “It looks like an alien,” she whispered.
When trying to imagine something we’ve never seen, we often default to something we have seen. For that reason, in our search for extraterrestrial life, we are usually looking for life as we know it. But is there a path for expanding our imagination to life as we don’t know it?
In physics, an analogous path was already established a century ago and turned out to be successful in many contexts. It involves conducting laboratory experiments that reveal the underlying laws of physics, which in turn apply to the entire universe. For example, around the same time when the neutron was discovered in the laboratory of James Chadwick in 1932, Lev Landausuggested that there might be stars made of neutrons. Astronomers realized subsequently that there are, in fact, some 100 million neutron stars in our Milky Way galaxy alone—and a billion times more in the observable universe. Recently, the LIGO experiment detected gravitational wave signals from collisions between neutron stars at cosmological distances. It is now thought that such collisions produce the precious gold that is forged into wedding bands. The moral of this story is that physicists were able to imagine something new in the universe at large and search for it in the sky by following insights gained from laboratory experiments on Earth.
Hot and humid The surface of a Hycean planet as interpreted by an artist. (Courtesy: Amanda Smith, University of Cambridge).
Topics: Astronomy, Astrophysics, Astrobiology, Exoplanets, Space Exploration
Hot, ocean-covered exoplanets with hydrogen-rich atmospheres could harbor life and may be more common than planets that are Earth-like in size, temperature, and atmospheric composition. According to astronomers at the University of Cambridge, UK, this newly defined class of exoplanets could boost the search for life elsewhere in the universe by broadening the search criteria and redefining which biosignatures are important.
Astronomers define the habitable or “Goldilocks” zone as the region where an exoplanet is neither too close nor too far from its host star to have liquid water on its surface – water being the perfect solvent for many forms of life. Previous studies of planetary habitability have focused primarily on searching for Earth-like exoplanets and evidence that they could harbor the kind of chemistry found in life on Earth. However, it has so far proven difficult to detect atmospheric signatures from Earth-like planets orbiting Sun-like stars.
Potentially habitable mini-Neptunes
Larger exoplanets are easier to detect than smaller, Earth-sized ones, and exoplanets around 1.6‒4 times bigger than the Earth, with masses of up to 15 Earth masses and temperatures that in some cases exceed 2000 K, are relatively common. These planets are known as mini-Neptune's as they are similar to the ice giant planets in our solar system.
Previous studies suggested that the high pressures and temperatures beneath these planets’ hydrogen-rich atmospheres were incompatible with life. However, based on their analysis of an exoplanet called K2-18b, exoplanet scientist Nikku Madhusudhan and colleagues at Cambridge say that life could, in fact, exist on a subset of mini-Neptunes that meet specific criteria.
This subset, which the researchers dub “Hycean” (hydrogen + ocean) planets, consists of planets that have radii up to 2.6 times larger than Earth’s and are capable of harboring vast oceans under atmospheres dominated by molecular hydrogen and water vapor. Such oceans could cover the whole planet and reach depths greater than the Earth’s oceans, and the researchers say that the conditions within them could be compatible with some forms of Earth-based microbial life. Hycean planets tidally locked with their host star could also exhibit habitable conditions on their permanent night side.
The origin of life is one of the great unanswered questions in science. One piece of this puzzle is that life started on Earth 4.5 billion years ago, just a few hundred million years after the formation of the Solar System, and involved numerous critical molecular components. How did all these components come to be available so quickly?
One potential explanation is that the Earth was seeded from space with the building blocks for life. The idea is that space is filled with clouds of gas and dust that contain all the organic molecules necessary for life.
Indeed, astronomers have observed these buildings blocks in interstellar gas clouds. They can see amino acids, the precursors of proteins, and the machinery of life. They can also see the precursors of ribonucleotides, molecules that can store information in the form of DNA.
But there is another crucial component for life – molecules that can form membranes capable of encapsulating and protecting the molecules of life in compartments called protocells. On Earth, the membranes of all cells are made of molecules called phospholipids. But these have never been observed in space. Until now.
The mysterious object ‘Oumuamua passed through our solar system in 2017. Loeb has suggested it could have been sent by extraterrestrials. (Credit: European Southern Observatory/Kornmesser)
Topics: Astrobiology, Biology, Cosmology, SETI
Life, for all its complexities, has a simple commonality: It spreads. Plants, animals, and bacteria have colonized almost every nook and cranny of our world.
But why stop there? Some scientists speculate that biological matter may have proliferated across the cosmos itself, transported from planet to planet on wayward lumps of rock and ice. This idea is known as panspermia, and it carries a profound implication: Life on Earth may not have originated on our planet.
In theory, panspermia is fairly simple. Astronomers know that impacts from comets or asteroids on planets will sometimes eject debris with enough force to catapult rocks into space. Some of those space rocks will, in turn, crash into other worlds. A few rare meteorites on Earth are known to have come from Mars, likely in this fashion.
“You can imagine small astronauts sitting inside this rock, surviving the journey,” says Avi Loeb, an astrophysicist at Harvard University and director of the school’s Institute for Theory and Computation. “Microbes could potentially move from one planet to another, from Mars to Earth, from Earth to Venus.” (You may recognize Loeb’s name from his recent book Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, which garnered headlines and criticism from astronomers for its claim that our solar system was recently visited by extraterrestrials.)</p>
Loeb has authored a number of papers probing the mechanics of panspermia, looking at, among other things, how the size and speed of space objects might affect their likelihood of transferring life. While Loeb still thinks it’s more likely that life originated on Earth, he says his work has failed to rule out the possibility that it came from somewhere else in space.
About 15 million years after the big bang, the entire universe had cooled to the point where the electromagnetic radiation left over from its hot beginning was at about room temperature. In a 2013 paper, I labeled this phase as the “habitable epoch of the early universe.” If we had lived at that time, we wouldn’t have needed the sun to keep us warm; that cosmic radiation background would have sufficed.
Did life start that early? Probably not. The hot, dense conditions in the first 20 minutes after the big bang produced only hydrogen and helium along with a tiny trace of lithium (one in 10 billion atoms) and a negligible abundance of heavier elements. But life as we know it requires water and organic compounds, whose existence had to wait until the first stars fused hydrogen and helium into oxygen and carbon in their interiors about 50 million years later. The initial bottleneck for life was not a suitable temperature, as it is today, but rather the production of the essential elements.
Given the limited initial supply of heavy elements, how early did life actually start? Most stars in the universe formed billions of years before the sun. Based on the cosmic star formation history, I showed in collaboration with Rafael Batista and David Sloan that life near sunlike stars most likely began over the most recent few billion years in cosmic history. In the future, however, it might continue to emerge on planets orbiting dwarf stars, like our nearest neighbor, Proxima Centauri, which will endure hundreds of times longer than the sun. Ultimately, it would be desirable for humanity to relocate to a habitable planet around a dwarf star like Proxima Centauri b, where it could keep itself warm near a natural nuclear furnace for up to 10 trillion years into the future (stars are merely fusion reactors confined by gravity, with the benefit of being more stable and durable than the magnetically confined versions that we produce in our laboratories).
I would extend his theme to cover something that comes naturally to us all, which I’ll call Pseudo-exceptionalism—the unearned conviction that we are exceptional, superior to others because we were born...us.
We simply assume that we’re kinder, more honest, more realistic, more wholesome than those around us. After all, we’re married to ourselves for life, so we make accommodations: We cut ourselves slack. We’re fast to forgive ourselves. When challenged, we’re much better at making our case than our opponent’s. We spot injustices to ourselves far faster than we spot our injustices to others.</em>
It is presumptuous to assume that we are worthy of special attention from advanced species in the Milky Way. We may be a phenomenon as uninteresting to them as ants are to us; after all, when we’re walking down the sidewalk we rarely if ever examine every ant along our path.
Our sun formed at the tail end of the star formation history of the universe. Most stars are billions of years older than ours. So much older, in fact, that many sunlike stars have already consumed their nuclear fuel and cooled off to a compact Earth-size remnant known as a white dwarf. We also learned recently that of order half of all sunlike stars host an Earth-size planet in their habitable zone, allowing for liquid water and for the chemistry of life.
Since the dice of life were rolled in billions of other locations within the Milky Way under similar conditions to those on Earth, life as we know it is likely common. If that is indeed the case, some intelligent species may well be billions of years ahead of us in their technological development. When weighing the risks involved in interactions with less-developed cultures such as ours, these advanced civilizations may choose to refrain from contact. The silence implied by Fermi's paradox (“Where is everybody?”) may mean that we are not the most attention-worthy cookies in the jar.
Cultural references: The post title refers to NC A&T Alumni, and Civil Rights icon Reverend Jesse Jackson's appearance on Saturday Night Live, and the Wow! signal. Personal note: This signal appeared on the same day my granddaughter was born.
<p>On April 29, 2019, the Parkes Radio Telescope in Australia began listing to the radio signals from the Sun’s nearest neighbor, Proxima Centauri, just over 4 lightyears away. The telescope was looking for evidence of solar flares and so listened for 30 minutes before retraining on a distant quasar to recalibrate and then pointing back.
In total, the telescope gathered 26 hours of data. But when astronomers analyzed it in more detail, they noticed something odd — a single pure tone at a frequency of 982.02 MHz that appeared five times in the data.
The signal was first reported last year in The Guardian, a British newspaper. The article raised the possibility that the signal may be evidence of an advanced civilization on Proxima Centauri, a red dwarf star that is known to have an Earth-sized planet orbiting in its habitable zone.
But researchers have consistently played down this possibility saying that, at the very least, the signal must be observed again before any conclusions can be drawn. Indeed, the signal has not been seen again, despite various searches.
Now Amir Siraj and Abraham Loeb from Harvard University in Cambridge, Massachusetts, have calculated the likelihood that the signal came from a Proxima Centauri-based civilization, even without another observation. They say the odds are so low as to effectively rule out the possibility — provided the assumptions they make in their calculations are valid.</p>
This artist’s concept shows a hypothetical planet covered in water around the binary star system of Kepler-35A and B. The composition of such water worlds has fascinated astronomers and astrophysicists for years. (Image by NASA/JPL-Caltech.)
Out beyond our solar system, visible only as the smallest dot in space with even the most powerful telescopes, other worlds exist. Many of these worlds, astronomers have discovered, may be much larger than Earth and completely covered in water — basically ocean planets with no protruding land masses. What kind of life could develop on such a world? Could a habitat like this even support life?
A team of researchers led by Arizona State University (ASU) recently set out to investigate those questions. And since they couldn’t travel to distant exoplanets to take samples, they decided to recreate the conditions of those water worlds in the laboratory. In this case, that laboratory was the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility at the DOE’s Argonne National Laboratory.
What they found — recently published in Proceedings of the National Academy of Sciences — was a new transitional phase between silica and water, indicating that the boundary between water and rock on these exoplanets is not as solid as it is here on Earth. This pivotal discovery could change the way astronomers and astrophysicists have been modeling these exoplanets, and inform the way we think about life evolving on them.
Dan Shim, associate professor at ASU, led this new research. Shim leads ASU’s Lab for Earth and Planetary Materials and has long been fascinated by the geological and ecological makeup of these distant worlds. That composition, he said, is nothing like any planet in our solar system — these planets may have more than 50% water or ice atop their rock layers, and those rock layers would have to exist at very high temperatures and under crushing pressure.
Lighter colors represent higher elevation in this image of Jezero Crater on Mars, the landing site for NASA's Mars 2020 mission. The oval indicates the landing ellipse, where the rover will be touching down on Mars. Credits: NASA/JPL-Caltech/MSSS/JHU-APL/ESA
Topics: Astrobiology, Mars, NASA, Space Exploration, Spaceflight
Scientists with NASA's Mars 2020 rover have discovered what may be one of the best places to look for signs of ancient life in Jezero Crater, where the rover will land on Feb. 18, 2021.
A paper published today in the journal Icarus identifies distinct deposits of minerals called carbonates along the inner rim of Jezero, the site of a lake more than 3.5 billion years ago. On Earth, carbonates help form structures that are hardy enough to survive in fossil form for billions of years, including seashells, coral and some stromatolites — rocks formed on this planet by ancient microbial life along ancient shorelines, where sunlight and water were plentiful.
The possibility of stromatolite-like structures existing on Mars is why the concentration of carbonates tracing Jezero's shoreline like a bathtub ring makes the area a prime scientific hunting ground.
Mars 2020 is NASA's next-generation mission with a focus on astrobiology, or the study of life throughout the universe. Equipped with a new suite of scientific instruments, it aims to build on the discoveries of NASA's Curiosity, which found that parts of Mars could have supported microbial life billions of years ago. Mars 2020 will search for actual signs of past microbial life, taking rock core samples that will be deposited in metal tubes on the Martian surface. Future missions could return these samples to Earth for deeper study.
Consider the possibility that an asteroid may have transformed the picture of life on Earth — but forget the dinosaurs and the massive crater, and rewind an extra 400 million years from that dramatic moment.
Back then, life was primarily an oceanic affair and backbones were the latest in arrival on the anatomy scene. But unlike the asteroid that killed the dinosaurs 66 million years ago, this earlier space rock never made it to Earth. Instead, a collision in the asteroid belt flooded the solar system with so much dust that, given some other changes at the time, allowed life on Earth to flourish, new research suggests.
"Most important events in the history of life are like that," said Rebecca Freeman, a paleontologist at the University of Kentucky who specializes in this period but wasn't involved in the new research. "You get a really unique set of circumstances that all come together, and you get a really dramatic event that maybe seems like it should be due to one particular dramatic thing. But in reality, it's a more complicated system at play," she told Space.com.
The dramatic event scientists want to explain is a spree of new species. That outburst of life, which paleontologists call the Great Ordovician Biodiversification Event, took place in the oceans, which were inhabited mostly by spineless creatures. "This is really a world that is dominated by invertebrate marine organisms," Freeman said. "Probably the top predator would have been a cephalopod," likely an ancestral relative of today's chambered nautilus, with its intricate spiral shell.
But when Birger Schmitz, a geologist at Lund University in Sweden, went hunting for rock dating back 466 million years, he wasn't hoping to find fossilized nautiluses; he was looking for fossilized meteorites. And over the past couple of decades, he and his colleagues have found dozens of these fossilized meteorites in a Swedish limestone quarry. Each carries a chemical time stamp indicating that it was heated about 470 million years ago, and scientists have thought for a while that there might have been a massive asteroid collision around that time.
The sea sloshing beneath the icy surface of Jupiter’s moon Europa just might be the best incubator for extraterrestrial life in our solar system. And yet it is concealed by the moon’s frozen outer shell—presenting a challenge for astrobiologists who would love nothing more than to peer inside. Luckily they can catch a partial glimpse by analyzing the flavor of the surface. And the results are salty.
A new study published this week in Science Advances suggests that sodium chloride—the stuff of table salt—exists on Europa’s surface. Because the exterior is essentially formed from frozen seawater, the finding suggests that Europa’s hidden sea is drenched in table salt—a crucial fact for constraining the possibilities for life on the alien world.
Not that scientists have tasted a slice of the distant moon. To analyze Europa’s composition, astronomers study the light emanating from its surface, splitting it into a rainbow-like spectrum to search for any telltale absorption or emission lines that reveal the world’s chemistry. There is just one problem: Ordinary table salt is white and thus gives off a featureless spectrum. But harsh radiation—which exists at Europa’s surface in abundance—just might add a dash of color. That much was realized in 2015 when two NASA planetary scientists Kevin Hand and Robert Carlson published a study suggesting the yellowish-brown gunk on Europa might be table salt baked by radiation. To reach that conclusion, Hand and Carlson re-created the conditions on Europa within vacuum chambers—or as Hand calls them, “stainless steel shiny objects that are humming and whizzing.” Next, they placed table salt into those chambers, lowered the pressures and temperatures to simulate Europa’s surface, and blasted the samples with an electron gun to simulate the intense radiation.
Topics: Astrobiology, Carl Sagan, Climate Change, Drake Equation, Existentialism, Fermi Paradox, Nuclear Power
“The universe is a pretty big place. If it's just us, seems like an awful waste of space.” Carl Sagan
My First Contact scenario doesn't involve Vulcans, warp drive or impossible scenarios: it involves radio transmissions, as communication is a big part of the Drake Equation. Specifically audio, video and digital data (Internet?) of extraterrestrial origin as we would confirm before announcing to the world. Assuming the aliens developed their technology in an oxygen-nitrogen environment, the language we could hear might amount to a lot of "clicking" noises, that mathematicians - specifically specialists in cryptography, and linguists - would dive into deciphering. Eventually after coming up with a Rosetta Stone of syntax, we could translate what would amount to news, drama and sitcoms. Of specific interest might be their political climate and sectarian strife (if any). More particularly, did they successfully translate through their "Great Filter"...
...or, if they did not.
I'm a big fan of Jordon Peele's incarnation of The Twilight Zone, particularly the sixth episode: "Six Degrees of Freedom." It is unfortunate that popular show title describes our current political climate.
I won't give away the intriguing ending, but Peele has mastered the macabre plot twist of Rod Serling's writing style, and (my opinion) his surreal monologue delivery. It's streaming, so you may have to pay less than you would for a single movie ticket per month to view it. I've enjoyed it andother shows so far, and I get no monetary gain for the endorsement.
"The Great Filter, in the context of the Fermi paradox, is whatever prevents dead matter from undergoing abiogenesis, in time, to expanding lasting life as measured by the Kardashev scale. The concept originates in Robin Hanson's argument that the failure to find any extraterrestrial civilizations in the observable universe implies the possibility something is wrong with one or more of the arguments from various scientific disciplines that the appearance of advanced intelligent life is probable; this observation is conceptualized in terms of a "Great Filter" which acts to reduce the great number of sites where intelligent life might arise to the tiny number of intelligent species with advanced civilizations actually observed (currently just one: human). This probability threshold, which could lie behind us (in our past) or in front of us (in our future), might work as a barrier to the evolution of intelligent life, or as a high probability of self-destruction. The main counter-intuitive conclusion of this observation is that the easier it was for life to evolve to our stage, the bleaker our future chances probably are.
The idea was first proposed in an online essay titled "The Great Filter - Are We Almost Past It?", written by economist Robin Hanson. The first version was written in August 1996 and the article was last updated on September 15, 1998. Since that time, Hanson's formulation has received recognition in several published sources discussing the Fermi paradox and its implications.
Using extinct civilizations such as Easter Island as models, a study conducted in 2018 posited that climate change induced by "energy intensive" civilizations may prevent sustainability within such civilizations, thus explaining the lack of evidence for intelligent extraterrestrial life." Source: Wikipedia/The Great Filter
The Great Filter is alluded to in science fiction with or without warp drive: Star Trek described global wars on Earth and the fictional Vulcan that involved their respective nuclear holocausts. For the Vulcans, recovery involved a relentless embrace of logic, or as I recall reading in a Trek novel, "reality-truth." For Earth, it essentially involved accepting help from the Vulcans after the human species was discovered warp capable through a singular genius with a funny name post self-induced Apocalypse, a Deus ex Machina plot device used since publicly performed Greek and Roman plays. We don't have warp drive, but we do have thermonuclear devices poised for Armageddon. We don't have Vulcans, but we once did have the Easter Islanders, just as once we had the Dodo.
I've often encapsulated The Great Filter in my own dictum: "intelligence is its own Entropy." I think when Carl Sagan was alive, the regressive forces we see now denying science, climate change; verifiable facts and reality were well engaged in his day of the original COSMOS. Slowly, shows like COSMOS lost their appeal to Game Shows cum Reality Shows, and as a country we reveled in our distractions, added as channels on cable and Internet multiplied like E. coli. and measles resurgenceas well as our grasp of what is real and verifiable. In fact, we seek distractions in gadgets and online machinations in the constant need to fill "horror vacui."
In the east, nothing meant something, particularly in clarity of thought: Mu Shin No Shin - "the mind without mind" or more colloquially, "no mind." As translated from the martial battlefield to artists both martial and objective; and Zen philosophers, it offers a certain clarity that can be attained when not focused on minutiae detail, but accepted reality "as-is" after diligent practice. A practice like karate forms that takes years of repetition, dedication and study. That is the key to mastering anything, from martial arts to science to civics.
The stars are silent. Intelligence may be rare. Vulcans if existing may not be benevolent, and in the myopic attention span of the erect species of which I am member - "wise men"...fleeting in longevity.