Artifacts In Space

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Voyager 2 entered interstellar space last month, becoming a space “artifact” of our civilization. (NASA)

 

All of a sudden, we have spacecraft and objects coming into our solar system and leaving for interstellar space. This is highly unusual, and very intriguing.

The departing spacecraft is Voyager 2, which launched in 1977 and has traveled spaceward some 11 billion miles.  It has now officially left the heliosphere, the protective bubble of particles and magnetic fields created by the sun.  In this it follows Voyager I – which left our solar system in 2012 — and managers of the two craft have reason to think they can travel until they cross the half-century mark.

This is taking place the same time that scientists are puzzling over the nature of a cigar-shaped object that flew into the solar system from interstellar space last year.

Nobody knows what the object – called Oumuamua, Hawaiian for “first messenger,” or “scout” – really is. The more likely possibilities of it being a comet or an solar system asteroid have been found to be inconsistent with some observed properties of the visitor, and this has led some senior scientists to even hypothesize that it just might be an alien probe.

The likelihood may be small, but it was substantial enough for Harvard University Astronomy Department Chairman Avi Loeb to co-author a paper presenting the possibility.  In the Astrophysical Journal Letters, Loeb and postdoc Shmuel Bialy wrote that the object “may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization.”

They also say the object has some characteristics of a “lightsail of artificial origins,” rather like the one that Loeb is working on as chairman of the Breakthrough Starshot advisory committee.  The well-funded private effort is hoping to develop ways to send a fleet of tiny lightsail probes to the star system nearest to us, Alpha Centauri.

 

This artist’s impression of the first detected interstellar visitor: Oumuamua. This object was discovered in October 2017 by the Pan-STARRS 1 telescope in Hawaii. Subsequent observations from ESO’s Very Large Telescope in Chile and other observatories around the world show that it was traveling through space for millions of years before its seemingly chance encounter with our star system.  But some scientists wonder:  might it be instead a probe sent into the cosmos by intelligent creatures?(NASA)

 

Put the two phenomenon together — the coming into our solar system and the going out — and you have a pathway into the world of alien “artifacts,” products of civilizations near and far.  They are the kind of “technosignatures,” the potential or actual handwork of intelligent beings, that NASA is now interested in learning about more.

We know this because during a fall conference in Houston convened by NASA at the request of members of Congress, scientists were brought together to discuss many different kinds of potential signs of intelligent extraterrestrial life.  While artifacts were one of many topics discussed, the term carries a quite magnetic pedigree.

So far, that meaning is of course fictional, or a misreading of actual features.  There is perhaps most famously the monoliths from the movie “2001: A Space Odyssey” and then the myriad sightings of alien spacecraft that turn out to be anything but that.

This image taken by VIking 1 in the mid 1970s led to years of discussion about Martian beings having at one time carved what appeared to be a gigantic face. (NASA)

 

And then there’s the “Face on Mars.”

The original image taken by Viking 1 looked somewhat like a human face. The feature, found in the region where the highlands meet the northern plains of Mars, was subsequently broadly popularized as a potential “alien artifact,” with even a major motion picture.

So many people were convinced that an image had been sculpted on the surface of Mars that NASA ultimately put out a substantial release in 2001 to make clear that the face was actually a mountain.

That was after the Mars Global Surveyor orbiter determined that the “face” was created by unusual reflections in an otherwise ordinary Martian mountain.

This high-resolution image from the Mars Orbiter Camera about the Mars Global Surveyor spacecraft shows the famous “Face on Mars” in detail, clearly showing it to be a natural geological formation. (NASA/MSSS)

 

 

So alien artifacts surely and properly have a steep hill to climb before they can be taken at all seriously.

But does that mean they shouldn’t be taken seriously at all?  Loeb clearly says no, that they are a potential source of important and compelling science, even if they are natural phenomena.

And then there’s the question raised in the Houston “technosignatures” conference:  What actually is meant by an artifact?

Longtime SETI scientist and advocate Jill Tarter, for instance, wondered if the signatures of intelligent civilizations could be imprinted on neutrinos.  She said that a leak of the radioactive isotope tritium, which has a short 12-year half-life,  could also signal the presence of advanced life because (unless it’s near a supernova) it would have to come quite recently from a nuclear reactor.

Taking it further, she and others argued that artifacts of intelligent life would include many atmospheric and planetary changes that could only be accomplished by intelligent beings.  For instance, the presence of unnatural pollutants such as chloroflurocarbons (CFCs) or sulfur hexafluoride (SF6) in an exoplanet atmosphere would, in this view, be an “artifact” of civilization.

Back, now, to Voyager 2, which is for sure an extraterrestrial artifact.

 

Rendering of Voyager 2 in deep space. (NASA/JPL)

 

Voyager 2 was launched by NASA in August, 1977 to study the outer planets.  Part of the larger Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune.

Both have traveled far their original destinations. The spacecraft were built to last five years and conduct close-up studies of Jupiter and Saturn.  With the spacecraft holding up despite the rigors,  additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible, and then the Voyagers were directed to interstellar space.

Their five-year lifespans have stretched to 41 years, making Voyager 2 NASA’s longest running mission ever.

At the on-going American Geophysical Union annual meeting, NASA project manager Suzanne Dodd said she believed that Voyager 2 can keep functioning for 5 to 10 more years in this new region of space, though not with all its instruments operating.

The greatest concerns about keeping the probes operating, she said, involve power and temperature. The  nuclear-powered Voyager 2 loses about 4 watts of power a year, and mission scientists have to shut off systems to keep instruments operating.

Voyager 2 is very cold — about 3.6 degrees Celsius and close to the freezing point of hydrazine — leading to concerns about the probe’s thruster that uses this fuel.  Dodd says she’s set a personal goal of keeping at least one of the Voyagers going until 2027, making it a 50-year mission.

The cameras for both probes are no longer on. But before the camera on Voyager 1 was decommissioned, it took the iconic “Pale Blue Dot” picture of the Earth.

 

 

This “Pale Blue Dot” image was captured in 1990, when Voyager 1 was about 4 million miles from Earth.  The spacecraft is now more than 13 billion miles from where it launched. (NASA)

 

In preparation for the potentially deep space travels for the Voyager spacecrafts, both were fitted with a greeting for any intelligent life that might be encountered.

The message is carried by a phonograph record – -a 12-inch gold-plated copper disk containing sounds and images selected to show the diversity of life and culture on Earth. The contents of the record were selected for NASA by a committee chaired by space scientist and popularizer Carl Sagan.  He and his associates assembled 115 images and a variety of natural sounds to give a sense of what Earth and Earthlings are like.

So are the Voyagers now artifacts from our civilization, messengers awaiting discovery by some distant beings?

Perhaps.  But they actually have not even left the solar system, and won’t be leaving anytime soon. They are in what is considered interstellar space, but the boundary of our solar system is beyond the outer edge of the Oort Cloud, a collection of small objects that are still under the influence of the sun’s gravity.

The width of the Oort Cloud is not known precisely, but it is estimated to begin at about 1,000 astronomical units (AU) from the sun and to extend to about 100,000 AU. One AU is the distance from the sun to Earth. It will take about 300 years for Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to fly beyond it.

 

The path of Oumuamua since it entered the solar system in 2017. (NASA)

 

Astronomers have long predicted that objects from other solar systems get shot out into space and arrive in our system.

The first identified interstellar object to visit our solar system, Oumuamua, was discovered in late 2017 by the University of Hawaii’s Pan-STARRS1 telescope as part of a NASA effort to search for and track asteroids and comets in Earth’s neighborhood.

While originally classified as a comet, observations revealed no signs of cometary activity after it was slingshotted around the sun at a remarkable 196,000 miles per hour.

Oumuamua seems to be a dark red highly-elongated metallic or rocky object that (at last analysis) is somewhere between 400 and 100 meters long and is unlike anything normally found in the solar system.  Researchers hypothesize that the shape and size suggest that the object has been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years.

Karen Meech of the University of Hawaii first identified Oumuamua. Here she is giving a TED Talk.

Immediately after its discovery, telescopes around the world were called into action to measure the object’s trajectory, brightness and color.  Combining the images from several large telescopes,  a team of astronomers led by Karen Meech of the Institute for Astronomy in Hawaii found that Oumuamua varies in brightness by a factor of 10 as it spins on its axis every 7.3 hours.

 

Avi Loeb, chair of the Harvard Astronomy Department and an advocate of thinking way outside the box about Oumuamua.

 

No known asteroid or comet from our solar system varies so widely in brightness, with such a large ratio between length and width. The most elongated objects we have seen to date are no more than three times longer than they are wide.

“This unusually big variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape,” said Meech. “We also found that it had a reddish color, similar to objects in the outer solar system, and confirmed that it is completely inert, without the faintest hint of dust around it.”

Oumuamua is headed out of the solar system now, so it’s unlikely more will be learned about it.  And with its odd shape and features, it clearly remains something of a mystery.

And that’s where Harvard’s Avi Loeb comes in.  Especially due to the remarkably fast speed with which Oumuamua entered the solar system, he argues that a probe sent by intelligent others cannot be ruled out, that science must be open minded.

“There is data on the orbit of this object for which there is no other explanation” than that it is the product of intelligent others,” he has said.  “The approach I take to the subject is purely scientific and evidence-based.”

Others strongly disagree.  But the views of the chairman of the Harvard astronomy department are nonetheless an intriguing part of the story.

 

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Does Proxima Centauri Create an Environment Too Horrifying for Life?

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Artist’s impression of the exoplanet Proxima Centauri b. (ESO/M. Kornmesser)

 

In 2016, the La Silla Observatory in Chile spotted evidence of possibly the most eagerly anticipated exoplanet in the Galaxy. It was a world orbiting the nearest star to the sun, Proxima Centauri, making this our closest possible exoplanet neighbour. Moreover, the planet might even be rocky and temperate.

Proxima Centauri b had been discovered by discerning a periodic wobble in the motion of the star. This revealed a planet with a minimum mass 30% larger than the Earth and an orbital period of 11.2 days. Around our sun, this would be a baking hot world.

But Proxima Centauri is a dim red dwarf star and bathes its closely orbiting planet in a level of radiation similar to that received by the Earth. If the true mass of the planet was close to the measured minimum mass, this meant Proxima Centauri b would likely be a rocky world orbiting within the habitable zone.

 

Comparison of the orbit of Proxima Centauri  b with the same region of the solar system. Proxima Centauri is smaller and cooler than the sun and the planet orbits much closer to its star than Mercury. As a result it lies well within the habitable zone. (ESO/M. Kornmesser/G. Coleman.)

Sitting 4.2 light years from our sun, a journey to Proxima Centauri b is still prohibitively long.

But as our nearest neighbor, the exoplanet is a prime target for the upcoming generation of telescopes that will attempt to directly image small worlds. Its existence was also inspiration for privately funded projects to develop faster space travel for interstellar distances.

Yet observations taken around the same time as the La Silla Observatory discovery were painting a very different picture of Proxima Centauri. It was a star with issues.

This set of observations were taken with Evryscope; an array of small telescopes that was watching stars in the southern hemisphere. What Evryscope spotted was a flare from Proxima Centauri that was so bright that the dim red dwarf star became briefly visible to the naked eye.

Flares are the sudden brightening in the atmosphere of a star that release a strong burst of energy. They are often accompanied by a large expulsion of plasma from the star known as a “coronal mass ejection”. Flares from the sun are typically between 1027 – 1032 erg of energy, released in a few tens of minutes.

For comparison, a hydrogen bomb releases the equivalent of about 10 megatons of TNT or a mere 4 x 1023 erg. Hitting the Earth, energy from solar flares and coronal mass ejections can disrupt communication equipment and create a spectacular aurora.

A solar flare erupting from the right side of the sun. (NASA/SDO)

But the Proxima super-flare spotted by Evryscope was well beyond a regular stellar flare.

On March 18 in 2016, this tiny red dwarf emitted an energy belch of 1033.5 erg. The flare consisted of one major event and three weaker ones and lasted approximately one hour, during which time Proxima Centauri became 68 times brighter.

A sudden, colossal increase in the brightness of a star does not bode well for any closely orbiting planets.

However, such a major flare might well be rare. If the star was normally fairly quiet, perhaps a planet could recover from a single very disruptive flare in the same way the Earth has survived mass extinction events.

Led by graduate student Ward Howard at the University of North Carolina, Chapel Hill, the discovering team used Evryscope to monitor Proxima Centauri for flares for a total of 1344 hours between January 2016 and March 2018. What they found was a horrifying environment, as reported in The Astrophysical Journal Letters.

While an event on the scale of the Proxima super-flare was only seen once, 24 large eruptions were spotted from the red dwarf, with energies from 1030.5 to 1032.4 erg. Allowing for the fact the star had only been observed for a small part of the year, this pattern of energy outbursts meant that a massive super-flare (1033 erg) was likely to occur at least five times annually.

 

Artist’s impression of the surface of the planet Proxima Centauri b. But what would conditions be like so close to a flaring star? (ESO/M. Kornmesser)

 

But how important is this for the planet?

The Earth is protected from flares from our sun by our atmosphere. The ozone layer absorbs harmful ultraviolet radiation with wavelengths between about 2400 – 2800 Angstroms (10-10 m), preventing it reaching the surface. So what if Proxima Centauri b had a similar protective layer of gases as the Earth?

To answer this question, Howard and his team ran simulations of an Earth-like atmosphere on Proxima Centauri b.

As is the case for the sun, the team assumed that large flares would be frequently accompanied by a coronal mass ejection. Radiation and stellar material then flooded over an Earth-like Proxima Centauri b at the observed rate. And the atmosphere crumbled.

 

Ward Howard, astrophysicist at the University of North Carolina.

High energy particles in the coronal mass ejections split the nitrogen molecules (N2) in the atmosphere, which reacted with the ozone (O3) to form nitrogen oxide (NO2). After just 5 years, 90% of the ozone in the atmosphere was lost and the amount was still decreasing.

Without ozone, the surface of Proxima Centauri b would be stripped of its protection from UV radiation. During the Proxima super-flare, the radiation dose without the protective ozone would be 65 times larger than that needed to kill 90% of one of the most UV-resilient organisms on Earth.

“Life would have to undergo extreme adaptation to UV or exist underground or underwater,” Howard notes. “Only the most resistant organisms could survive on the surface in this environment.”

The simulation does assume that Proxima Centauri b does not have a magnetic field. Such a shield could channel the particles from the coronal mass ejection to the poles, forming the aurora as on Earth and reducing the damage to the atmosphere.

However, orbiting so close to the star, Proxima Centauri b is likely to be in tidal lock as the moon is to the Earth. This is expected to weaken the magnetic field, as the slower rotation makes it harder to create a magnetic dynamo within the planet.

So if the protective shields are lowered on Proxima Centauri b, is our nearest planet a world populated by highly resistant UV organisms? Or have we seen evidence that rather than warming the planet to allow life to exist, this star has snuffed it out?

 

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Technosignatures and the Search for Extraterrestrial Intelligence

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A rendering of a potential Dyson sphere, named after Freeman A. Dyson. As proposed by the physicist and astronomer decades ago, they would collect solar energy on a solar system wide scale for highly advanced civilizations. (SentientDevelopments.com)

The word “SETI” pretty much brings to mind the search for radio signals come from distant planets, the movie “Contact,” Jill Tarter, Frank Drake and perhaps the SETI Institute, where the effort lives and breathes.

But there was a time when SETI — the Search for Extraterrestrial Intelligence — was a significantly broader concept, that brought in other ways to look for intelligent life beyond Earth.

In the late 1950s and early 1960s — a time of great interest in UFOs, flying saucers and the like — scientists not only came up with the idea of searching for distant intelligent life via unnatural radio signals, but also by looking for signs of unexpectedly elevated heat signatures and for optical anomalies in the night sky.

The history of this search has seen many sharp turns, with radio SETI at one time embraced by NASA, subsequently de-funded because of congressional opposition, and then developed into a privately and philanthropically funded project of rigor and breadth at the SETI Institute.  The other modes of SETI went pretty much underground and SETI became synonymous with radio searches for ET life.

But this history may be about to take another sharp turn as some in Congress and NASA have become increasingly interested in what are now called “technosignatures,” potentially detectable signatures and signals of the presence of distant advanced civilizations.  Technosignatures are a subset of the larger and far more mature search for biosignatures — evidence of microbial or other primitive life that might exist on some of the billions of exoplanets we now know exist.

And as a sign of this renewed interest, a technosignatures conference was scheduled by NASA at the request of Congress (and especially retiring Republican Rep. Lamar Smith of Texas.)  The conference took place in Houston late last month, and it was most interesting in terms of the new and increasingly sophisticated ideas being explored by scientists involved with broad-based SETI.

“There has been no SETI conference this big and this good in a very long time,” said Jason Wright, an astrophysicist and professor at Pennsylvania State University and chair of the conference’s science organizing committee.  “We’re trying to rebuild the larger SETI community, and this was a good start.”

 

At this point, the search for technosignatures is often likened to that looking for a needle in a haystack. But what scientists are trying to do is define their haystack, determine its essential characteristics, and learn how to best explore it. (Wiki Commons)

 

During the three day meeting in Houston, scientists and interested private and philanthropic reps. heard talks that ranged from the trials and possibilities of traditional radio SETI to quasi philosophical discussions about what potentially detectable planetary transformations and by-products might be signs of an advanced civilization. (An agenda and videos of the talks are here.)

The subjects ranged from surveying the sky for potential millisecond infrared emissions from distant planets that could be purposeful signals, to how the presence of certain unnatural, pollutant chemicals in an exoplanet atmosphere that could be a sign of civilization.  From the search for thermal signatures coming from megacities or other by-products of technological activity, to the possible presence of “megastructures” built to collect a star’s energy by highly evolved beings.

Michael New is Deputy Associate Administrator for Research within NASA’s Science Mission Directorate. He was initially trained in chemical physics. (NASA)

All but the near infrared SETI are for the distant future — or perhaps are on the science fiction side — but astronomy and the search for distant life do tend to move forward slowly.  Theory and inference most often coming well before observation and detection.

So thinking about the basic questions about what scientists might be looking for, Wright said, is an essential part of the process.

Indeed, it is precisely what Michael New, Deputy Associate Administrator for Research within NASA’s Science Mission Directorate, told the conference. 

He said that he, NASA and Congress wanted the broad sweep of ideas and research out there regarding technosignatures, from the current state of the field to potential near-term findings, and known limitations and possibilities.

“The time is really ripe scientifically for revisiting the ideas of technosignatures and how to search for them,” he said.

He offered the promise of NASA help  (admittedly depending to some extent on what Congress and the administration decide) for research into new surveys, new technologies, data-mining algorithms, theories and modelling to advance the hunt for technosignatures.

 

Crew members aboard the International Space Station took this nighttime photograph of much of the Atlantic coast of the United States. The ability to detect the heat and light from this kind of activity on distant exoplanets does not exist today, but some day it might and could potentially help discover an advanced extraterrestrial civilization. (NASA)

 

Among the several dozen scientists who discussed potential signals to search for were the astronomer Jill Tarter, former director of the Center for SETI Research, Planetary Science Institute astrobiologist David Grinspoon and University of Rochester astrophysicist Adam Frank.  They all looked at the big picture, what artifacts in atmospheres, on surfaces and perhaps in space that advanced civilizations would likely produce by dint of their being “advanced.”

All spoke of the harvesting of energy to perform work as a defining feature of a technological planet, with that “work” describing transportation, construction, manufacturing and more.

Beings that have reached the high level of, in Frank’s words, exo-civilization produce heat, pollutants, changes to their planets and surroundings in the process of doing that work.  And so a detection of highly unusual atmospheric, thermal, surface and orbital conditions could be a signal.

One example mentioned by several speakers is the family of chemical chloroflourocarbons (CFCs,)  which are used as commercial refrigerants, propellants and solvents.

Astronomer Jill Tarter is an iconic figure in the SETI world and led the SETI Institute for 30 years. (AFP)

These CFCs are a hazardous and unnatural pollutant on Earth because they destroy the ozone layer, and they could be doing something similar on an exoplanet.  And as described in the conference, the James Webb Space Telescope — once it’s launch and working — could most likely detect such an atmospheric compound if it’s in high concentration and the project was given sufficient telescope time.

A similar single finding described by Tarter that could be revolutionary is the radioactive isotope tritium, which is a by-product of the nuclear fusion process.  It has a short half-life and so any distant discovery would point to a recent use of nuclear energy (as long as it’s not associated with a recent supernova event, which can also produce tritium.)

But there many other less precise ideas put forward.

Glints on the surface of planets could be the product of technology,  as might be weather on an exoplanet that has been extremely well stabilized, modified planetary orbits and chemical disequilibriums in the atmosphere based on the by-products of life and work.  (These disequilibriums are a well-established feature of biosignature research, but Frank presented the idea of a technosphere which would process energy and create by-products at a greater level than its supporting biosphere.)

Another unlikely but most interesting example of a possible technosignature put forward by Tarter and Grinspoon involved the seven planets of the Trappist-1 solar system, all tidally locked and so lit on only one side.  She said that they could potentially be found to be remarkably similar in their basic structure, alignment and dynamics. As Tarter suggested, this could be a sign of highly advanced solar engineering.

 

Artist rendering of the imagined Trappist-1 solar system that had been terraformed to make the planets similar and habitable.  The system is one of the closest found to our own — about 40 light years.

 

Grinspoon seconded that notion about Trappist-1, but in a somewhat different context.

He has worked a great deal on the question of today’s anthropocene era — when humans actively change the planet — and he expanded on his thinking about Earth into the galaxies.

Grinspoon said that he had just come back from Japan, where he had visited Hiroshima and its atomic bomb sites, and came away with doubts that we were the “intelligent” civilization we often describe ourselves in SETI terms.  A civilization that may well self destruct — a fate he sees as potentially common throughout the cosmos — might be considered “proto-intelligent,” but not smart enough to keep the civilization going over a long time.

Projecting that into the cosmos, Grinspoon argued that there may well be many such doomed civilizations, and then perhaps a far smaller number of those civilizations that make it through the biological-technological bottleneck that we seem to be facing in the centuries ahead.

These civilizations, which he calls semi-immortal, would develop inherently sustainable methods of continuing, including modifying major climate cycles, developing highly sophisticated radars and other tools for mitigating risks, terraforming nearby planets, and even finding ways to evolve the planet as its place in the habitable zone of its host star becomes threatened by the brightening or dulling of that star.

The trick to trying to find such truly evolved civilizations, he said, would be to look for technosignatures that reflect anomalous stability and not rampant growth. In the larger sense, these civilizations would have integrated themselves into the functioning of the planet, just as oxygen, first primitive and then complex life integrated themselves into the essential systems of Earth.

And returning to the technological civilizations that don’t survive, they could produce physical artifacts that now permeate the galaxy.

 

MeerKAT, originally the Karoo Array Telescope, is a radio telescope consisting of 64 antennas now being tested and verified in the Northern Cape of South Africa. When fully functional it will be the largest and most sensitive radio telescope in the southern hemisphere until the Square Kilometre Array is completed in approximately 2024. (South African Radio Astronomy Observatory)

 

This is exciting – the next phase Square kilometer Array (SKA2) will be able to detect Earth-level radio leakage from nearby stars. (South African Radio Astronomy Observatory)

 

While the conference focused on technosignature theory, models, and distant possibilities, news was also shared about two concrete developments involving research today.

The first involved the radio telescope array in South Africa now called MeerKAT,  a prototype of sorts that will eventually become the gigantic Square Kilometer Array.

Breakthrough Listen, the global initiative to seek signs of intelligent life in the universe, would soon announce the commencement of  a major new program with the MeerKAT telescope, in partnership with the South African Radio Astronomy Observatory (SARAO).

Breakthrough Listen’s MeerKAT survey will examine a million individual stars – 1,000 times the number of targets in any previous search – in the quietest part of the radio spectrum, monitoring for signs of extraterrestrial technology. With the addition of MeerKAT’s observations to its existing surveys, Listen will operate 24 hours a day, seven days a week, in parallel with other surveys.

This clearly has the possibility of greatly expanded the amount of SETI listening being done.  The SETI Institute, with its radio astronomy array in northern California and various partners, have been listening for almost 60 years, without detecting a signal from our galaxy.

That might seem like a disappointing intimation that nothing or nobody else is out there, but not if you listen to Tarter explain how much listening has actually been done.  Almost ten years ago, she calculated that if the Milky Way galaxy and everything in it was an ocean, then SETI would have listened to a cup full of water from that ocean.  Jason Wright and his students did an updated calculation recently, and now the radio listening amounts to a small swimming pool within that enormous ocean.

 

The NIROSETI team with their new infrared detector inside the dome at Lick Observatory. Left to right: Remington Stone, Dan Wertheimer, Jérome Maire, Shelley Wright, Patrick Dorval and Richard Treffers. (Laurie Hatch)

The other news came from Shelley Wright of the University of California, San Diego, who has been working on an optical SETI instrument for the Lick Observatory and beyond.

She has developed a Near-Infrared Optical SETI (NIROSETI)  instrument designed to search for signals from extraterrestrials at near-infrared wavelengths — a first. The near-infrared is an excellent spectral region to search for signals from extraterrestrials, since it offers a unique window for interstellar communication.  NIROSETI is now operating 8 to 12 nights per month, overseen by students at a remote location.

In addition, Wright and Harvard University’s Paul Horowitz have been working on a novel instrument for searching the full sky all the time for very short pulses of light — an idea that came out of a Breakthrough Listen meeting in 2016. The pulses they are searching for are nanosecond to one second bursts which,  could only come from technological civilizations.

This PANOSETI (Pulsed All-sky Near-infrared Optical SETI)  uses a most unusual light-collection method that features some 100 compact, wide-viewing Fresnel lenses mounted on two small geodesic domes, and connected to the telescope at the Lick Observatory. I

Jason Wright is an assistant professor of astronomy and astrophysics at Penn State. His reading list is here.

Jason Wright of Penn State was especially impressed by the project, which he said in the future can look at much of the sky at once and was put together with on very limited budget.

Wright, who teaches a course on SETI at Penn State and is a co-author of a recent paper trying to formalize SETI terminology, said his own take-away from the conference is that it may well represent an important and positive moment in the history of technosignatures.

“Without NASA support, the whole field has lacked the normal structure by which astronomy advances,” he said.  “No teaching of the subject, no standard terms, no textbook to formalize findings and understandings.

“The SETI Institute carried us through the dark times, and they did that outside of normal, formal structures. The Institute remains essential, but hopefully that reflex identification will start to change.”

 

Participants in the technosignatures conference in Houston last month, the largest SETI gathering in years.  And this one was sponsored by NASA and put together by the NExSS for Exoplanet Systems Science (NExSS,)  an interdisciplinary agency initiative. (Delia Enriquez)
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Time-Traveling in the Australian Outback in Search of Early Earth

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This story was written by Nicholas Siegler, Chief Technologist for NASA’s Exoplanet Exploration Program at the Jet Propulsion Laboratory with the help of doctoral student Markus Gogouvitis, at the University of New South Wales, Australia and Georg-August-University in Gottingen, Germany.

 

These living stromatolites at Shark Bay, Australia are descendants of similar microbial/sedimentary forms once common around the world.  They are among the oldest known repositories of life.  Most stromatolites died off long ago, but remain at Shark Bay because of the high salinity of the water. (Tourism, Western Australia)

 

This past July I joined a group of geologists, geochemists, microbiologists, and fellow astronomers on a tour of some of the best-preserved evidence for early life.

Entitled the Astrobiology Grand Tour, it was a trip led by Dr. Martin Van Kranendonk, a structural geologist from the University of New South Wales, who had spent more than 25 years surveying Australia’s Pilbara region. Along with his graduate students he had organized a ten-day excursion deep into the outback of Western Australia to visit some of astrobiology’s most renowned sites.

The trip would entail long, hot days of hiking through unmaintained trails on loose surface rocks covered by barb-like bushes called spinifex.  As I was to find out, nature was not going to give up its secrets easily.  And there were no special privileges allocated to astrophysicists from New Jersey.

 

The route of our journey back in time.  (Google Earth/Markus Gogouvitis /Martin Van Kranendonk)

The state of Western Australia, almost four times the size of the American state of Texas but with less than a tenth of the population (2.6 million), is the site of many of astrobiology’s most heralded sites. For more than three billion years, it has been one of the most stable geologic regions in the world.

It has been ideal for geological preservation due to its arid conditions, lack of tectonic movement, and remoteness. The rock records have in many places survived and are now able to tell their stories (to those who know how to listen).

 

The classic red rocks of the Pilbara in Western Australia, with the needle sharp spinifex bushes in the foreground. (Nick Siegler, NASA/JPL-Caltech)

Our trip began with what felt like a pilgrimage. We left Western Australia’s largest city Perth and headed north for Shark bsy. It felt a bit like a pilgrimage because the next morning we visited one of modern astrobiology’s highlights – the living stromatolites of Shark Bay.

Stromatolites literally mean “layered rocks”. It’s not the rocks that are alive but rather the community of microbial mats living on top. They are some of the Earth’s earliest ecosystems.

We gazed over these living microbial communities aloft on their rock perches and marveled at their exceptional longevity — the species has persisted for over three billion years. Their ancestors had survived global mass extinctions, planet-covering ice glaciers, volcanic activity, and all sorts of predators. Once these life forms took hold they were not going to let go.

 

The stromatolites forming today in the shallow waters of Shark Bay, Australia are built by colonies of microbes that capture ocean sediments. (University of Wisconsin-Madison)

The photosynthetic bacteria that built ancient stromatolites played a central role of our trip for three reasons:

  • Their geological footprints allowed scientists to date the evolution of early life and at times gain insight into the environments in which they grew.
  • They eventually harbored the first oxygen-producing bacteria and played a central role in creating our oxygen-rich atmosphere.
  • By locating ever-increasingly older microbial fossils we observed a lower limit to the age of the first life forms.. Given photosynthesis is not a simple process, the first life forms must have been simpler. Speculating, perhaps a few hundred million years earlier so that the first life form on Earth may have originated at four billion years ago.

When viewed under a microscope, you can see the mats are made of millions of single cell bacteria and archaea, among the simplest life forms we know. Within these relatively thin regions are multiple layers of specialized microbial communities that live interdependently.

Bacteria in the top layer evolved to harvest sunlight to live and grow via photosynthesis. Their waste products include oxygen as well as important nutrients for many different bacterial species within underlying layers. And this underlying layer’s waste product would do the same for the layer beneath it, perfectly recycling each other’s waste. The oldest forms of life that we know of had learned to co-exist together in a chemically interdependent environment.

 

Broken piece of a living stromatolite, which was was remarkably spongy and smelled slightly salty, indicative of the hypersaline bay that has contributed to their survival by making bacteria and other organisms undesirable. What was actually most remarkable of the visit to Hamelin pool was how quiet it was. There were no seagulls and other birds because of the hypersaline environment. They had gone elsewhere for their meals. (Nick Siegler, NASA/JPL-Caltech)

 

We saw ripped up portions of the mats that washed upon the shore at Hamelin pool in Shark Bay. A whole ecosystem held in one’s hand. Thousands of millions of years ago ancient relatives of these microbes thrived in shallow waters all around our planet, and left behind fossilized remains. But due to the evolution of grazing organisms these microbial structures are nowadays constrained to very specific environments. In the case of Shark Bay, the very high salt contents of this inlet have warded off most predators providing the microbes with a safe haven to live.

Ironically, the rocks, which help identify these ancient life forms, at the time were just a nuisance for the living microbes.

Small fine grains of sedimentary rock carried along in the daily tides would occasionally get stuck in the sticky mucus the microbes would secrete. In addition, the photosynthetic bacteria found at Shark Bay may have been inadvertently making their own rock by depleting the carbon dioxide in the surrounding water as part of photosynthesis and precipitating carbonate, adding to the grains of sediment trapped within the sticky top layer.

Over time, the grains from both the sedimentary and precipitated rocks would  cover the surface and block the sunlight for which these organisms had evolved to depend on. As an evolutionary tour de force, the photosynthetic microbes learned to migrate upward, leaving the newly formed rock layers behind.

These secondary rock fossils today showcase visually observable crinkly, frequently conical shapes, in stark contrast to abiotic sedimentary rocks. These ancient life forms left behind geological footprints reminding us they were here first.

Nick Siegler of JPL on his Australian Magical Origins Tour.  (Markus Gogouvitis)

Now to the most important contribution of stromatolites – terraforming the Earth.

Living in shallow water, the top most layer of the Shark Bay microbial mats are known to host cyanobacteria, photosynthetic bacteria that produce oxygen as a byproduct. Scientists don’t know what the first bacteria produced as they harnessed the energy of the Sun. But they do know that they eventually started producing oxygen.

In the evolution of life that eventually led to all plants and animals, this was one of the great events. More than 2.5 billion years ago, ancient bacteria began diligently producing oxygen in the oceans. Earth’s atmosphere began to irreversibly shift from its original, oxygen-free existence, to an oxic one, initiating the formation of our ozone layer and paving the way for the evolution of more complex life. Our planet has been terraformed by micro-organisms!

It was in the Karijini National Park where we went back in time (2.4 billion years) and observed an extraordinary piece of evidence for the early production of oxygen in Earth’s oceans, a time before oxygen made a strong presence in our atmosphere.

 

Banded iron formation at Karajini National Park.  (Nick Siegler, NASA-JPL/Caltech)

 

We saw a massive gorge with steep vertical walls carved out by flowing water. As oxygen production by early bacteria increased below the water surface it would react with dissolved iron ions (early oceans were iron-rich) causing iron oxides to precipitate and settle to the bottom.

For reasons not entirely understood — perhaps related to seasonal or temperature effects– the amount of new oxygen temporarily decreased and iron ion remained soluble in the oceans and other types of sediments accumulated, carbonates, slate, and shale. And then, just as before, the oxygen reappeared creating a new layer of precipitated iron.

The result was a banded sedimentary rock, a litmus test to a changing world, where oxygen would be the reactive ingredient leading to larger and more complex life forms. As the oxygen production no longer cycled, the oxygen went on to saturate the ocean and then accumulated in the Earth’s atmosphere eventually to the levels we have today.

 

Banded iron formation at Karajini. (Nick Siegler, NASA-JPL/Caltech)

After a day of looking down at rocks and spinifex it was both a relief and a joy to look up at the glorious Western Australian night sky. Far away from the light pollution of modern cities, each night would greet us with an awe-inspiring starlit sky. It never got old to remember we are part of a vast network of stars suspended in an infinite space.

The nights would start with the appearance of Venus well before sundown followed shortly by the innermost planet Mercury and then Jupiter and Saturn. It didn’t take long after sunset to see the renowned Southern Cross. Mars joined the evening as well, perfectly appearing on the arc called the ecliptic.

But nothing stirred the group more than the emergence of the swath of stars of the Milky Way, the disk of our home galaxy where its spiral arms all lie. The nights would be so clear that one could actually see the dark clouds of gas and dust that block large portions of the galaxy’s stars from shining through. We partook in the well-known tradition connecting individual points of light to form exotic creatures like scorpions and centaurs. But we also we followed the inverted approach of the Aborigines and connected the dark patches. Only then did we see the emu of the Milky Way. I would never have thought of connecting the darkness.

 

Australian night sky, with campfire below.  (Maëva Millan/NASA-GSFC/Georgetown University)

The night sky appeared even more special knowing that each of its stellar members likely host planetary systems like our own. How many of them host life? Maybe even civilizations? The numbers are in their favor.

At the half-way point of our trip we hiked to an ancient granite region in the red rocks of the Pilbara which contain the world’s largest concentration of Pleistocene rock art also known as petroglyphs. These etchings are believed to be 6,000 to 20, 000 years old.

The artists used no pigments, but rather rocks to pound/chisel shapes into the desert varnish, a thin dark film (possibly of microbial origin) that typically covers exposed rock surfaces in hyper arid regions. We came across many stylized male and female figures with highlighted genitalia as well as animals such as emus and kangaroos. Little is known about the people who created these art works. They left no clues to their origin or fate.

 

Rock art by aboriginal people done 6,000 to 20,000 years ago. The shapes were etched into an existing varnish on the rock. (Nick Siegler, NASA-JPL/Caltech)

Pilbara is also where the oldest mineral on Earth –a zircon dated at 4.4 billion years old — was discovered four years ago in the Jack Hills region.  Because of the geological history of the region, it is a frequent (if hardscrabble) site where many geologists and geochemists specializing in ancient Earth do their work.

In the last several days of the tour we encountered ever-increasing older evidence of stromatolites extending out to circa 3.5 billion years, about 75% of the history of the Earth. I expected the quality of the stromatolites to degrade as we went back in time and it looked like I was right until I saw a remarkably large rock in a locality called the Strelley Pool Formation. The rock measuring approximately 1.5 meters in all three directions gave a rare view of ancient stromatolites from all sides and an unequivocal interpretation of past life.

Large and ancient fossil stromatolite at the Strelley Pool Formation, with Siegler and Gogouvitis.  (Nick Siegler, NASA-JPL/Caltech)

The shapes of the embedded rocks formed by the microbial mats from the top view clearly show the elliptical areas where the bacteria inched upwards to acquire sunlight. Regions between the conical stromatolites were filled in by carbonate sediments in ancient shallow waters. These were later chemically altered to silica-rich rocks through alteration and etching of minerals by fluids. Silicified rocks are very weather-resistant, making them a great medium to preserve fossils for billions of years.

The side views of the stromatolite-laden rock revealed the expected conical layered shapes we saw in younger rocks (and in the living stromatolites of Shark Bay). Everything we had learned about stromatolite structures was clearly visible in this circa 3.43 billion year old example. It is astounding to realize that complex phototrophic (light-eating) organisms, even if not yet oxygen producing, were around during the deposition of the Strelley Pool Formation.

 

Detail of Strelley Pool stromatolite fossil.  (Nick Siegler, NASA-JPL/Caltech)

It is not unreasonable to speculate that the earliest life forms are even older by perhaps a few more hundred million years or so. There is evidence for even more ancient stromatolites in Greenland (3.7 billion years old) and isotope carbon evidence, with considerable controversy, in Nuvvuagittuq greenstone belt in northern Quebec, Canada (4.28 billion years old). Hence, life on Earth may have emerged within 500 million years from its formation. That is astonishingly rapid.

Was Earth an exception or the rule? What does that say for possible life on exoplanets?

Our tour came to an end on July 11. We had traveled over 1,600 miles through Australia’s outback, from Western Australia’s biggest city Perth, all the way up to Port Hedland at the north coast. We were privileged to see the country in ways that very few people get a chance to, and to be steeped in the multidisciplinary sciences of astrobiology while seeing some of its iconic ground.

I had seen some of the earliest evidence for life and the pivotal effect it had on our environment. For those 10 days I learned what it was like to be a time traveler.

 

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Water Worlds, Aquaplanets and Habitability

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This artist rendering may show a water world — without any land — or an aquaplanet with lots of more shallow water around a rocky planet. (NASA)

 

The more exoplanet scientists learn about the billions and billions of celestial bodies out there, the more the question of unusual planets — those with characteristics quite different from those in our solar system — has come into play.

Hot Jupiters, super-Earths, planets orbiting much smaller red dwarf stars — they are all grist for the exoplanet mill, for scientists trying to understand the planetary world that has exploded with possibilities and puzzles over the past two decades.

Another important category of planets unlike those we know are the loosely called “water worlds” (with very deep oceans) and their “aquaplanet” cousins (with a covering of water and continents) but orbiting stars very much unlike our sun.

Two recent papers address the central question of habitability in terms of these kind of planets — one with oceans and ice hundreds of miles deep, and one particular and compelling planet (Proxima Centauri b, the exoplanet closest to us) hypothesized to have water on its surface as it orbits a red dwarf star.

The question the papers address is whether these watery worlds might be habitable.  The conclusions are based on modelling rather than observations, and they are both compelling and surprising.

In both cases — a planet with liquid H20 and ice many miles down, and another that probably faces its red dwarf sun all or most of the time — the answers from modelers is that yes, the planets could be habitable.   That is very different from saying they are or even might be inhabited.  Rather,  the conclusions are based on computer models that take into account myriad conditions and come out with simulations about what kind of planets they might be.

This finding of potential watery-world habitability is no small matter because predictions of how planets form point to an abundance of water and ice in the planetesimals that grow into planets.

As described by Eric Ford, co-author of one of the papers and a professor of astrophysics at Pennsylvania State University, “Many scientists anticipate that planets with oceans much deeper than Earths could be a common outcome of planet formation. Indeed, one of the puzzling properties of Earth is that it has oceans that are just skin deep” compared to the radius of the planet.

“While some planets very close to their star might loose all their water, it would take a delicate balancing act to remove many ocean’s worth of water and to leave a planet with oceans as shallow as those on Earth.”

An interesting place to start.

 

Artist’s conception of a planet covered with a global ocean. A new study finds that these wate rworlds could maintain stable climates and perhaps sustain life under certain conditions. (ESO/M. Kornmesser)

 

It should first be said that many scientists are dubious that extreme water worlds can support life or can support detectable life.  My colleague Elizabeth Tasker wrote a column — Can You Overwater a Planet? — focused on this view last year.

The first of the two new exoplanets/ocean papers involves planets with very deep oceans. Written by Edwin Kite of the University of Chicago and Ford of Penn State, the paper in the Astrophysical Journal concludes that even a planet with such super deep oceans could — under certain conditions — provide habitable conditions.

This finding is at odds with previous simulations, and Kite says that is part of its significance. The scientific community has largely assumed that planets covered in a deep ocean would not support the cycling of minerals and gases that keeps the climate stable on Earth, and thus wouldn’t be friendly to life.

But the Kite and Ford study found that ocean planets (with 10 to 1000 times as much water as Earth) could remain habitable much longer than previously assumed. The authors performed more than a thousand simulations to reach that conclusion.

Eric Ford is a professor astrophysics at Penn State and a specialist in planet formation. (Penn State)

“This really pushes back against the idea you need an Earth clone—that is, a planet with some land and a shallow ocean,” said Edwin Kite, assistant professor of geophysical sciences at the University of Chicago and lead author of the study.

Edwin Kite is an assistant professor of planetary sciences at the University of Chicago. (Univ. of Chicago)

Because life needs an extended period to evolve — and because the light and heat on planets can change as their stars age — scientists usually look for planets that have both some water and some way to keep their climates stable over time. The method for achieving this steady state that we know is, of course, how it works on Earth. Over eons, our planet has cooled itself by drawing down atmospheric greenhouse gases into minerals and warms itself up by releasing them via volcanoes.

But this model doesn’t work on a water world, with deep water covering the rock and suppressing volcanoes.

Kite and Ford wanted to know if there was another way to achieve a balance. They set up a simulation with thousands of randomly generated planets, and tracked the evolution of their climates over billions of years.

“The surprise was that many of them stay stable for more than a billion years, just by luck of the draw,” Kite said. “Our best guess is that it’s on the order of 10 percent of them.”

These planets sit in the right location around their stars. They happened to have the right amount of carbon present, and they don’t have too many minerals and elements from the crust dissolved in the oceans that would pull carbon out of the atmosphere. They have enough water from the start, and they cycle carbon between the atmosphere and ocean only, which in the right concentrations is sufficient to keep things stable.

None of this means that such a planet exists — our ability to detect oceans worlds is in its infancy.  The issue is rather that Kite and Ford conclude that a deep ocean planet could potentially be habitable if other conditions were met.

 

Artist rendering of Proxima Centauri b orbiting its red dwarf host star. (ESO/L.Calçada/Nick Risinger)

 

Anthony Del Genio and his team of modelers at NASA’s Goddard Institute for Space Studies in New York used their state-of-the-art climate simulations to look at another aspect of the exoplanet water story, and they chose Proxima Centauri b as their subject.  The roughly Earth-sized planet was discovered in 2016 and is the closest exoplanet to Earth.

Scientists determined early on that it is a rocky (as opposed to gaseous) planet and that it orbits its host star every 11 days.  If that star was as powerful as our sun, there would be no talk of possible habitability on close-in Proxima b.  But the star is a red dwarf and puts out only a fraction of the radiation coming from a host star like our sun.

Still, the case for habitability on Proxima b was initially considered to be weak, in part because the planet is tidally locked by its closeness to the host star.  In other words, it would most likely not spin to create days and nights as it orbits, but rather would have a sun-facing side and a space-facing side — making the temperature differences great.

Our ability to characterize a small planet like Proxima b remains very limited, and so it is unknown whether the planet has water or whether it has an atmosphere.  So those two essential components of the habitability question are missing.

But Del Genio’s team decided to model the dynamics of Proxima b with a presumed ocean, though not one that is many miles deep.  In Earth science parlance, what Del Genio referred to as an “aquaplanet.” And using their sophisticated models, they would simulate “dynamic” oceans with currents like our own, rather than the stationary oceans modeled earlier on exoplanets.

And rather to their surprise, they reported in the journal Astrobiology that their model of ocean behavior showed that the planet would not have only small areas of potential habitability — the earlier proposed habitable “eyeball” scenario — but rather much of the planet could be habitable.  That could include some of the normally space-facing side.

 

One type of possible water world is an “eyeball” planet, where the star-facing side is able to maintain a liquid-water ocean, while the rest of the surface is ice. (Image via eburacum45/DeviantArt)

 

“Our group said let’s hook up an atmosphere to a dynamic ocean rather than a static one,” Del Genio said.  “That way you get ocean currents like those on our coasts, and they move water of different temperatures around.

“If you have a real and dynamic ocean in your model, then we found that the eyeball goes away.  Usually the currents go west to east and they carry warmer water even to the night side.”

Anthony Del Genio, leader of NASA’s GISS team that  uses cutting edge Earth climate models to better understand conditions on exoplanets.

So using this more sophisticated model, not insignificant areas of Proxima b, or any other planet like it orbiting a red dwarf star, could be habitable, they concluded.  But again, that is assuming some pretty big “ifs” — the presence of an ocean and an atmosphere.

And then the team added variables such as a thick nitrogen and carbon atmosphere or a thin one, fresh water or salty water, a planet that is firmly locked and never rotating, or one that rotates a modest amount — giving the dark side some light.  Del Genio said that with all these added factors, a substantial portion of the surface of Proxima b, or a planet like it, would have liquid water and potentially habitable conditions.

This focus on watery worlds — including those that would be extreme compared with Earth today — makes sense in the context of the history of Earth.

While there is no direct evidence of this, many scientists think that the very early Earth was covered for a period of time with water with little or no land.

And then after land appeared, it still took some three billion years for any life form — bacteria, early planets — to colonize the land, and another half billion years for animals to come ashore.  Yet the oceans were long habitable and inhabited, as early a 3.8 billion years ago.

So until astronomy and exoplanet science develop the needed instruments and scientists acquire the observed knowledge of conditions on water worlds, progress will come largely from modelling that tells us what might be possible.

 

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