Category: The Search for Life Beyond Earth (page 1 of 7)

Sure UFOs Exist. But There’s No Reason To Conclude That Aliens Are Flying Them

An apparently unidentified object detected on a Navy plane’s infrared camera. (U.S. Department of Defense/Navy Times)

It seems to happen with some regularity.  Claims that Unidentified Flying Objects are visiting us have captured the public imagination once more and a big reveal is expected soon.

That will come, oddly, from a government report required to be released by the end of June that will supposedly detail the many sightings made by high-flying military pilots and unexplained detections by satellites.  The requirement was added to the Covid relief package that was passed by Congress in December and orders the Department of Defense and the Office of the DIrector of National Intelligence to release their unclassified findings on the subject, information that has been apparently collected for decades.

In terms of national defense, these reports could indeed be meaningful.  If other nations are sending

This well known poster was first introduced during an episode of the 1990s television show, “The X Files.” and featured in a subsequent movie.

drones or satellites of some sort (true UFOs) to get close to and study American assets, then that’s important news.

But, of course, the UFO drama is overwhelmingly about something else:  The claimed presence of intelligent aliens that are scoping out Earth for reasons ranging from awe-inspiring or extremely worrisome.

The report — which sources say concludes that there is insufficient evidence to confirm or conclusively rule out extraterrestrial UFO sightings —  will no doubt be widely consumed by a population with many “UFO believers.”  After all, a 2019 Gallup poll found that 33 percent of American adults said that alien spacecraft from distant planets and galaxies have been visiting us.

I find all this to be not only unfortunate but also misguided and potentially damaging.  The moment will pass with no intelligent aliens identified, and then will return again some time in the future for another round.

The potential damage is to the very real, very challenging, very cutting-edge science being conducted around the world that seeks to identify actual signs of actual extraterrestrial life in the cosmos, or at least to know what to look for when we have space telescopes and instruments with the necessary power.

And I’m concerned that a focus on UFOs imagined to be carrying intelligent alien life takes away from the hard-won seriousness of their enormous and so compelling scientific effort.  This is especially true now that the scientific search for extraterrestrial life is on the front burner for the National Academy of Sciences, which will soon make recommendations about a next grand observatory for the 2030s.… Read more

Breakthrough Listen Searches The Crowded Center of the Milky Way for Possible Signals From Intelligent Beings

The Galactic Center from radio to X-ray frequencies.  ( X-Ray: NASA, CXC, UMass, D. Wang et al.; Radio: NRF, SARAO, MeerKAT)

Searching for technologically advanced civilizations inhabiting distant exoplanets is the astrobiological equivalent of swinging for the fences.

While much of the search of extraterrestrial life is now focused on microbes and chemical biosignatures in exoplanet atmospheres that would likely be byproducts of life, the search for extraterrestrial intelligence (or SETI) takes a very different approach.

SETI practitioners scan the skies for radio signals, and now laser signals, that are irregular and different from what is naturally produced.  Were such a signal to be detected, then it would be studied as the potential work of extraterrestrial life that is highly advanced — perhaps far more so than we Earthlings.

This search has been going on since Cornell University astronomer Frank Drake began it 1960 and has advanced (in steps large and small) ever since.  The biggest financial boost to the search took place five years ago when techno-billionaire Yuri Milner, in partnership with Stephen Hawking and other prominent scientists,  set up the Breakthrough Listen project with $100 million to buy telescope time and to greatly expand the SETI search.

And as part of that expanded search, radio telescopes focused on the crowded galactic center of the Milky Way for 600 observing hours.  The thinking was that stars and likely exoplanets are most plentiful in that central region — some 60 million  stars in the line of sight into the galactic center at low astronomical frequencies; 500,000 at higher frequencies  — and so the chances of finding a signal were perhaps higher.

Some preliminary and partial results of that effort were recently released and, unfortunately, no signals were found.  That has been the fate of all SETI searches so far.

But as SETI scientists explain, the night sky is huge and the percentage of stars (and their exoplanets) that have been sampled remains quite small.

The Green Bank Radio Observatory in West Virginia is one of the two main sites for the Breakthrough Listen galactic center campaign.  The other is the Parkes Telescope in Australia . (NRAO)

This latest effort was unique in that it was the “most sensitive and deepest targeted SETI” survey ever done of the galactic center, as the SETI scientists write in a study set to be published in the Astronomical Journal (a preprint is currently available on the arXiv).… Read more

The Hows and Whys of Mars Sample Return

Combining two images, this mosaic shows a close-up view of the rock target named “Yeehgo” taken by the SuperCam instrument on NASA’s Perseverance rover on Mars. To be compatible with the rover’s software, “Yeehgo” is an alternative spelling of “Yéigo,” the Navajo word for diligent.

One of the fondest dreams and top priorities of space science for years has been  to bring a piece of Mars back to Earth to study in the kind of depth possible only in a cutting-edge laboratory.

While the instruments on Mars rovers can tell us a lot,  returning a sample to study here on Earth is seen as the  way to ultimately tease out the deepest secrets of the composition of Mars, its geological and geochemical history and possibly the presence of life, life fossils or of the precursor molecules  of life.

But bringing such a sample to Earth is extraordinarily difficult.  Unlike solar system bodies that have been sampled back on Earth — the moon, a comet and some asteroids — Mars has the remains of an atmosphere.  That means any samples would have to lift off in a rocket brought to Mars and with some significant propulsive power, a task that so far has been a technical bridge too far.

That is changing now and the Mars Sample Return mission has begun.  The landing of the Perseverance rover in Jezero Crater on Mars signaled that commencement and the rover will be used to identify, drill into and collect intriguing bits of Mars.  This is a long-term project, with the best case scenario seeing those Mars samples arriving on Earth in a decade.  So this entirely unprecedented, high-stakes campaign will be playing out for a long time.

“I think that Mars scientists would like to return as much sample as possible,” said Lindsay Hays, NASA Mars Sample Return deputy program scientist.  “Being able to return samples that we collected with purpose is how we take the next step in our exploration of Mars.”

“And it seems that there are still so many unknowns, even in our solar system, even with the planets right next door, that every time we do something new, we answer a couple of questions that we hoped to and but also find a whole bunch of new things that we never expected.”

“I am so excited to see what comes of this adventure.  And I think that is a feeling shared by Mars scientists and planetary scientists broadly.”… Read more

The Space Telescope That Could Find a Second Earth

This rare picture of an exoplanet (called 2M1207B) shows a red world several times Jupiter’s size orbiting a brown dwarf much smaller and dimmer than our sun. LUVOIR is after more elusive targets: small, rocky planets around bright stars. (ESO)

What will it take to capture images and spectra of a distant world capable of harboring life?
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For all the excitement surrounding the search for distant exoplanets in recent years, the 4,000-plus planets confirmed so far have been unseen actors on the cosmic stage. Except for a handful of very large bodies imaged by ground-based telescopes, virtually all exoplanets have been detected only when they briefly dim the light coming from their host stars or when their gravity causes the star to wobble in a distinctive way. Observing these patterns and using a few other methods, scientists can determine an exoplanet’s orbit, radius, mass, and sometimes density—but not much else. The planets remain, in the words of one researcher in the field, “small black shadows.”

Scientists want much more. They’d like to know in detail the chemical makeup of the planets’ atmospheres, whether liquid water might be present on their surfaces, and, ultimately, whether these worlds might be hospitable to life.

Answering those questions will require space telescopes that don’t yet exist. To determine what kinds of telescopes, NASA commissioned two major studies that have taken large teams of (mostly volunteer) scientists and engineers four years to complete. The results are now under review by the National Academy of Sciences, as part of its Decadal Survey for Astronomy and Astrophysics that will recommend government funding priorities for the 2030s. Past and current NASA mega-projects, from the Hubble Space Telescope launched in 1990 to the James Webb Space Telescope, which is scheduled for launch this year, have all gone through this same vetting process. Sometime this spring, the Decadal Survey is expected to wrap up its deliberations and make recommendations.

That puts four proposals in the running to become NASA’s next “Great Observatory” in space: an X-ray telescope called Lynx; the Origins Space Telescope for studying the early universe; and two telescopes devoted mostly, but not exclusively, to exoplanets. One is called HabEx, for Habitable Exoplanet Observatory. The other—the most ambitious, most complex, most expensive, and most revolutionary of all these concepts—is called LUVOIR, for Large UV/Optical/IR Surveyor.… Read more

NASA’s Perseverance Rover Lands on Mars — The Third Martian Arrival in a Week

This true-color Mars globe includes Terra Meridiani, the region where NASA’s Opportunity rover explored from 2004 to 2018.  Two more Mars rovers — one from NASA and the other from China — are scheduled to land this week and then later in the year. (NASA/Greg Shirah)

Mars is receiving visitors these days.  Quite a few of them.

The most prominent visitor is NASA’s Perseverance rover,  which made a difficult but smooth precision landing at 3.55 ET  this afternoon.

The rover now sits in Jezero Crater, in an area that clearly once had lots of water flowing.   The site was selected, in part, because the Perseverance rover’s official mission includes — for the first time since the mid 1970s — an effort to find signs of long ago life.

Perseverance will join the Curiosity rover on Mars, that pioneering machine that has revolutionized our understanding of the planet since it landed in 2012  The Curiosity and Perseverance rovers are similar in design but carry different instruments with different goals.

A key difference:  Curiosity was tasked with determining whether Mars had once been habitable and found that it definitely had been, with flowing rivers, large lakes and necessary-for-life organic compounds.  Perseverance will take another scientific step forward and search for signs that Mars actually was once inhabited.

Perseverance also joins China’s Tianwen-1 (“heavenly questions”) probe,  which went into orbit around Mars last week.  It is the first Chinese spacecraft to arrive at Mars, and later this spring or summer the Chinese space agency will attempt to land a rover as well on the planet’s northern plains..

And then there’s the Hope spacecraft which entered into Mars orbit last week as well.  Launched by the United Arab Emirates, it was placed in a wide orbit so it could study the planet’s weather and climate systems, which means it also can see the full planet in one view.

These spacecraft will join several others on or orbiting Mars, making this by far the busiest time ever for exploration of Mars — a real milestone.

NASA’s Perseverance rover will land in Jezero Crater. This image was produced using instruments on NASA’s Mars Reconnaissance Orbiter, which helps identify potential landing sites for future missions. On ancient Mars, water carved channels and transported sediments to form fans and deltas within lake basins, as is clearly visible at here at Jezaro Crater (NASA/JPL-Caltech/ASU)

That the Perseverance mission has a formal goal of searching for ancient signs of life is a big deal, and involves a lot of history.… Read more

How Radioactive Elements May Make Planets Suitable or Hostile to Life

An artist’s conception of a super Venus planet on the left and a super Earth on the right.  The question of what makes one planet habitable and one uninhabitable is a focus of many astrobiology researchers.  A new hypothesis looks at the presence of radioactive elements as an important factor in making a solar system habitable. (NASA/JPL-Caltech/Ames)

When describing exoplanets that are potentially promising candidates for life, scientists often use the terminology of the “habitable zone.”  This is a description of planets in orbit where temperatures, as predicted by the distance from the host star,  are not too cold for liquid water to exist on a planetary surface and also not to hot for all the water to burn off.

This planetary sweet spot, which not surprisingly Earth inhabits, is also more casually called the “Goldilocks zone” for exoplanets.

While there is certainly value to the habitable zone concept, there has also been scientific pushback to using the potential presence of liquid water as a primary or singular factor in predicting potential habitability.

There are just too many other factors that can play into habitability, some argue, and a focus on a planet’s distance from its host sun (and thus its temperature regime) is too narrow.  After all, several of the objects that just might support life in our own solar system are icy moons quite far from any solar system habitable zone.

With these concerns in the background, an interdisciplinary team of astrophysicists and planetary scientists at the University of California, Santa Cruz has begun to look at a source of heat in addition to suns and tidal forces that might play a role in making a planet habitable.

This source is the heat generated by the decay of long-lived radioactive elements such as uranium, thorium and potassium, which are found in stars and presumably on and in planets throughout the galaxies in greater or lesser amounts.

Using theory and modeling, they have concluded that the abundance of these radioactive elements in a planetary mantle can indeed give important insights into whether life might emerge there.

Supercomputer models of Earth’s magnetic field,  which is kept going thanks in part to the heat and subsequent convection produced by radioactive decay. (NASA)

Uranium is among the most widespread  elements on Earth — 500 times more common than gold It is present on the surface and in the mantle below. (Atomic Heritage Foundation.)

Read more

Strong Doubts Arise About the Reported Phosphine Biosignature in the Atmosphere of Venus

An artist’s depiction of Venus and, in the inset, phosphine molecules.
(© ESO/M. Kornmesser/L. Calçada & NASA/JPL-Caltech,)

What started as a stunning announcement that the chemical phosphine — a known byproduct of life — had been found in the clouds of Venus and could signal the presence of some lifeform has now been strongly critiqued by a number of groups of scientists.   As a result, there is growing doubt that the finding, published in the journal Nature Astronomy in September,  is accurate.

The latest critique, also submitted to Nature Astronomy but available in brief before publication, is led by NASA’s planetary scientist Geronimo Villaneuva and others at the Goddard Space Flight Center. They reanalyzed the data used to reach the conclusion that phosphine was present and concluded that the signal was misinterpreted as phosphine and most likely came instead from sulphur dioxide, which Venus’s atmosphere is known to contain in large amounts.

The title of their paper is “No phosphine in the atmosphere of Venus.”

Another paper led by Ignas Snellen from the Leiden Observatory came to a similar conclusion, but finding fault elsewhere. She and her team analyzed the data used in the initial research to see if cleaning up the noise with a 12-variable mathematic formula, as was used in the paper, could lead to incorrect results.

According to Snellan, using this formula actually gave the original team —  false results and they found “no statistical evidence for phosphine in the atmosphere of Venus.”

While this critical research does not on its own disprove that phosphine exists in Venus’ atmosphere, it clearly raises doubts about original team’s conclusions.

That original team was lead by Jane S. Greaves, a visiting scientist at the University of Cambridge when when she worked on the phosphine finding.  She herself has also has been unable to replicate the level of phosphine found by her team, and was a co-author on a paper that described that.   It is now almost impossible to collect new data because of the coronavirus pandemic.


Venus is roughly the size of Earth but much hotter due to its huge concentrations of carbon dioxide in the atmosphere.  (NASA)

This intense scrutiny continues as staff at the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, discovered a separate, unspecified issue in the data that were used to detect the phosphine. “There are some issues with interpretation that we are looking at,” says Dave Clements, an astrophysicist at Imperial College London and co-author of the original study.… Read more

Could Life Exist in the Clouds of Venus?

Nightside of Venus captured with the IR2 (infrared) camera on JAXA’s Akatsuki climate orbiter (JAXA).

On September 14 at 3pm GMT, an embargo lifted on a research paper reporting evidence for biological activity on Venus. Speculation about the discovery had been spreading rapidly through social media for several days, proving that scientists are incapable of keeping secrets.

With a surface temperature sufficient to melt lead, Venus is not the usual candidate for extraterrestrial life. However, the reported signature resides not on the surface of the planet, but in its clouds.

Led by Professor Jane Greaves at Cardiff University, the research team report an observation of phosphine; a molecule consisting of one atom of phosphorous and three atoms of hydrogen (PH3). On Earth, the trace amounts of phosphine in the atmosphere all come from either human or microbial activity. But does that make the presence of phosphine irrefutable evidence of life on Venus?

The case for phosphine as a biosignature

Phosphine has been found in the atmospheres of the gas giant planets, Jupiter and Saturn. However, this phosphine forms at the high temperatures and pressures existing deep within the giants’ colossal hydrogen-rich atmospheres. This process is not possible on the terrestrial planets, where the atmospheres are vastly thinner and hydrogen poor.

Instead of hydrogen, Venus’s atmosphere consists predominantly of carbon dioxide with clouds of sulfuric acid. While both ingredients sound abysmal for the prospect of life, the molecules consist of carbon and sulfur bounded to oxygen atoms. The prevalence of oxygen atoms should have resulted in any phosphorous present in the atmosphere to chemically react in a similar fashion to form a phosphate molecule (phosphorous and oxygen), rather than the observed phosphine (phosphorus and hydrogen).

Surface photographs from the former Soviet Union’s Venera 13 spacecraft, which touched down in March 1982. Temperatures on the surface are sufficient to melt lead, while the sulfur in the clouds gives the air its yellow/orange colour (NASA).

Despite considering thousands of possible reactions that might occur within Venus’s atmosphere, Greaves and her team failed to simulate the production of phosphine on Venus through abiotic (non-biological) means. Energetic processes such as lightening, volcanic activity or delivery via meteorites were also ruled out as possible sources, as the quantities they produced should be too low to explain the detection.

Estimates for the lifetime of phosphine also remove the chance that the molecules are leftover from an earlier epoch when the young Venus hosted a more clement environment.… Read more

How Many Habitable Zone Planets Can Orbit a Host Star?

This representation of the Trappist-1 system shows which planets could potentially have temperature conditions which would allow for the presence of liquid water, seen generally as essential for life.  The inner three planets are likely too hot, and the outer planet is probably too cold, but the middle three planets might be just right. (NASA / JPL-Caltech)

Our solar system has but one planet orbiting in what is commonly known as the habitable zone — at a distance from the host star where water could be liquid at times rather than always ice or gas.  That planet, of course, is Earth.

But from a theoretical, dynamical perspective, does this always have to be the case?  The answer to that question is no because a number of stars are known to have more than one habitable zone planet.

Now a team from the University of California, Riverside has produced a study that concludes as many as seven Earth-sized, habitable zone planets could orbit a single star — if there were no large Jupiter-sized planets in the system and if the star was of a particular type.

The article, published in the Astronomical Journal, concluded that seven habitable zone planets was the maximum for a star, but a sun such as ours could potentially support six planets with sometimes liquid water — a condition considered essential for life.

Study leader Stephen Kane, an astrobiologist who focuses on potentially habitable exoplanets, said he had been studying the nearby solar system Trappist-1, which has three Earth-like planets in its habitable zone and seven planets all together.

“This made me wonder about the maximum number of habitable planets it’s possible for a star to have, and why our star only has one,” Kane said.

With the discovery of an eighth planet, the Kepler-90 system is the first to tie with our solar system in number of planets. Artist’s concept. Credit: NASA/Ames Research Center/Wendy Stenzel

His conclusion:

“Even though (our solar system) only has one planet in the habitable zone, it’s not necessarily the typical situation. A far more typical scenario may be to have many planets in the habitable zone, depending on the presence of a giant planet.”

More later about the destabilizing effects of giant planet, but the Kane (and others) say that looking for solar systems without Jupiter-size planets has become increasingly important because of this effect on other terrestrial planets.

To determine how many habitable zone planets might be possible in a solar system, his team created a model system in which they simulated planets of various sizes orbiting their stars.

Read more

For First Time, Tiny CubeSat Locates a Distant Exoplanet


The image above, courtesy of NASA’s Jet Propulsion Laboratory, shows the CubeSat ASTERIA as it was being launched from the International Space Station in 2017.

The size of a briefcase, ASTERIA is part of a growing armada of tiny spacecraft being launched around the world and adding an increasingly important (and inexpensive) set of new tools for conducting Earth, space and exoplanet science.

ASTERIA, for instance, was designed to perform some of the complex tasks much larger space observatories use to study distant exoplanets outside our solar system.   And a new paper soon to be published in the Astronomical Journal describes how ASTERIA (short for Arcsecond Space Telescope Enabling Research in Astrophysics) didn’t just demonstrate it could perform those tasks but went above and beyond, detecting the known exoplanet 55 Cancri e.

While it was not the first detection of that exoplanet — which orbits close to its host star 41 light years away — it was the first time that a CubeSat had measured the presence of an exoplanet, something done so far only by much more sophisticated space and ground telescopes.

“Detecting this exoplanet is exciting because it shows how these new technologies come together in a real application,” said Vanessa Bailey, who led the ASTERIA  exoplanet science team at JPL.  The project was a collaboration between JPL and the Massachusetts Institute of Technology.

“We went after a hard target with a small telescope that was not even optimized to make science detections – and we got it, even if just barely,” said Mary Knapp, the ASTERIA project scientist at MIT’s Haystack Observatory and lead author of the study. “I think this paper validates the concept that motivated the ASTERIA mission: that small spacecraft can contribute something to astrophysics and astronomy.”  Both made their comments in a JPL release.


Artist rendering of planet Cancri 55 e. (NASA; JPL/Caltech)


ASTERIA was originally designed to spend 90 days in space.  But it received three mission extensions before the team lost contact with the satellite in late 2019.

The mission was not even designed to look for exoplanets.  It was, rather, a technology demonstration, with the mission’s goal to develop new capabilities for future missions. The team’s technological leap was to build a small spacecraft that could conduct fine pointing control — essentially the ability to stay focused very steadily on a distant star for long periods.… Read more

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