Many Worlds

Author: Marc Kaufman (page 1 of 15)

“Agnostic Biosignatures,” And the Path to Life as We Don’t Know It

August 12, 2019 / / 0 Comments

Most research into signs of life in our solar system or on distant planets uses life on Earth as a starting point. But now NASA has begun a major project to explore the potential signs of life very different from what we have on Earth.  For example, groups of molecules, like those above, can be analyzed for complexity, regardless of their specific chemical constituents.  ( Brittany Klein/Goddard Space Flight Center)

Biosignatures – evidence that says or suggests that life has been present – are often very hard to find and interpret.

Scientists examining fossilized life on Earth can generally reach some sort of agreement about what is before them, but what about the soft-bodied or even single-celled organisms that were the sum total of life on Earth for much of the planet’s history as a living domain? Scientific disagreements are common.

Now think of trying to determine whether a particular outline on an ancient Martian rock, or a geochemical or surface anomaly on that rock, is a sign of life. Or perhaps an unexpected abundance of a particular compound in one of the water vapor plumes coming out of the moons Europa or Enceladus. Or a peculiar chemical imbalance in the atmosphere of a distant exoplanet as measured in the spectral signature collected via telescope.

These are long-standing issues and challenges, but they have taken on a greater urgency of late as NASA missions  (and those of other space agencies around the world) are being designed to actively look for signs of extraterrestrial life – most likely very simple life – past or present.

And that combination of increased urgency and great difficulty has given rise to at least one new way of thinking about those potential signs of life. Scientists call them “agnostic biosignatures” and they do not presuppose any particular biochemistry.

“The more we explore the solar system and distant exoplanets, the more we find worlds that are really foreign,”  said Sarah Stewart Johnson, at an assistant professor at Georgetown University and principal investigator of the newly-formed Laboratory for Agnostic Biosignatures (LAB).  The LAB team won a five-year, $7 million grant last year from NASA’s Astrobiology Program.

“So our goal is to go beyond our current understandings and find ways to explore the world of life as we don’t know it,” she told me.  “That might mean thinking about a spectrum of how ‘alive’ something might be… And we’re embracing uncertainty, looking as much for biohints as biosignatures.”

Johnson first visited the acid salt lakes of the Yilgarn Craton of Western Australia as a graduate student at MIT, and has returned multiple with colleagues to understand mineral biosignatures as well as biomarker preservation in this analog environment for early Mars.

… Read more

Exoplanets Discoveries Flood in From TESS

August 1, 2019 / / 0 Comments

NASA’s Transiting Exoplanet Survey Satellite (TESS) has hundreds of “objects of interest” waiting to be confirmed as planets in the data from the space telescope’s four cameras.  These three were the first confirmed TESS discoveries, identified last year during its first three months of observing. By the time the mission is done, TESS’s wide-field cameras will have covered the whole sky in search of transiting exoplanets around 200,000 of the nearest (and brightest) stars. (NASA / MIT / TESS)

The newest space telescope in the sky — NASA’s Transiting Exoplanet Survey Satellite, TESS — has been searching for exoplanets for less than a year, but already it has quite a collection to its name.

The TESS mission is to find relatively nearby planets orbiting bright and stable suns, and so expectations were high from the onset about the discovery of important new planets and solar systems.  At a meeting this week at the Massachusetts Institute of Technology devoted to TESS  results,  principal investigator George Ricker pronounced the early verdict.

The space telescope, he said,  “has far exceeded our most optimistic hopes.”  The count is up to 21 new planets and 850 additional  candidate worlds waiting to be confirmed.

Equally or perhaps more important is that the planets and solar systems being discovered promise important results.  They have not yet included any Earth-sized rocky planet in a sun’s habitable zone — what is generally considered the most likely, though hardly the only, kind of planet to harbor life — but they did include planets that offer a great deal when it comes to atmospheres and how they can be investigated.

This infographic illustrates key features of the TOI 270 system, located about 73 light-years away in the southern constellation Pictor. The three known planets were discovered by NASA’s Transiting Exoplanet Survey Satellite through periodic dips in starlight caused by each orbiting world. Insets show information about the planets, including their relative sizes, and how they compare to Earth. Temperatures given for TOI 270’s planets are equilibrium temperatures, (NASA’s Goddard Space Flight Center/Scott Wiessinger)

One of the newest three-planet system is called TOI-270, and it’s about 75 light years from Earth. The star at the center of the system is a red dwarf, a bit less than half the size of the sun.

Despite its small size, it’s brighter than most of the nearby stars we know host planets. And it’s stable, making its solar system especially valuable.

… Read more

If Bacteria Could Talk

July 29, 2019 / / 0 Comments

 

Hawaiian lava cave microbial mats appear to have the highest levels and diversity of genes related to quorum sensing so far.  (Stuart Donachie, University of Hawai`i at Mānoa)

Did you know that many bacteria — some of the oldest lifeforms on Earth — can talk?  Really.

And not only between the same kind of single-cell bacteria, but  back and forth with members of other species, too.

Okay, they don’t talk in words or with sounds at all.  But they definitely communicate in a meaningful and essential way, especially in the microbial mats and biofilms (microbes attached to surfaces surrounded by mucus) that constitute their microbial “cities.”

Their “words” are conveyed via chemical signaling molecules — a chemical language — going from one organism to another,  and are a means to control when genes in the bacterial DNA are turned “on” or “off.”  The messages can then be translated into behaviors to protect or enhance the larger (as in often much, much larger) group.

Called “quorum sensing,” this microbial communication was first identified several decades ago.  While the field remains more characterized by questions than definitive answers, is it clearly growing and has attracted attention in medicine, in microbiology and in more abstract computational and robotics work.

Most recently,  it has been put forward as chemically-induced behavior that can help scientists understand how bacteria living in extreme environments on Earth — and potential on Mars —  survive and even prosper.  And the key finding is that bacteria are most successful when they form communities of microbial mats and biofilms, often with different species of bacteria specializing in particular survival capabilities.

Speaking at the recent Astrobiology Science Conference in Seattle,  Rebecca Prescott, a National Science Foundation  Postdoctoral Research Fellow in Biology said this community activity may make populations of bacteria much more hardy than otherwise might be predicted.

 

Quorum sensing requires a community. Isolated Bacteria (and Archaea) have nobody to communicate with and so genes that are activated by quorum sensing are not turned “on.”

“To help us understand where microbial life may occur on Mars or other planets, past or present, we must understand how microbial communities evolve and function in extreme environments as a group, rather than single species,” said Prescott,

“Quorum sensing gives us a peek into the interactive world of bacteria and how cooperation may be key to survival in harsh environments,” she said.

Rebecca Prescott  is a National Science Foundation Postdoctoral Fellow in Biology (1711856) and is working with principal investigator Alan Decho of the University of South Carolina on a NASA Exobiology Program grant.

… Read more

Curiosity Rover as Seen From High Above by Mars Orbiter

July 13, 2019 / / 0 Comments

A camera on board NASA’s Mars Reconnaissance Orbiter recently spotted the Curiosity rover in Gale Crater.  The image is color-enhanced to allow surface features to become more visible. (NASA/JPL-Caltech)

This is Apollo memory month, when the 50th anniversary arrives of the first landing of astronauts on the moon.  It was a very big deal and certainly deserves attention and applause.

But there’s something unsettling about the anniversary as well, a sense that the human exploration side of NASA’s mission has disappointed and that its best days were many decades ago.   After all, it has been quite a few years now since NASA has been able to even get an astronaut to the International Space Station without riding in a Russian capsule.

There have been wondrous (and brave) NASA human missions since Apollo — the several trips to the Hubble Space Telescope for emergency repair and upgrade come to mind — but many people who equate NASA with human space exploration are understandably dismayed.

This Many Worlds column does not focus on human space exploration, but rather on the science coming from space telescopes, solar system missions, and the search for life beyond Earth.

And as I have argued before, the period that following the last Apollo mission and began with the 1976 Viking landings on Mars has been — and continues to be — the golden era of space science.

This image of Curiosity,  which is now exploring an area that has been named Woodland Bay in Gale Crater, helps make the case.

Taken on May 31 by the HiRISE camera of NASA’s Mars Reconnaissance Orbiter (MRO), it shows the rover in a geological formation that holds remains of ancient clay.  This is important because clay can be hospitable to life, and Curiosity has already proven that Mars once had the water, organic compounds and early climate to support life.

The MRO orbits between 150 and 200 miles above Mars, so this detailed image is quite a feat.

The arm of the Curiosity rover examines the once-watery remains at Woodland Bay, Gale Crater. (NASA/JPL-Caltech)

Curiosity landed on Mars for what was planned as a mission of two years-plus. That was seven years ago this coming August.

The rover has had some ups and downs and has moved more slowly than planned, but it remains in motion — collecting paradigm-shifting information, drilling into the Mars surface, taking glorious images and making its way up the slopes of Gale Crater. … Read more

NASA Announces Astrobiology Mission to Titan

June 27, 2019 / / 1 Comment

 

The Dragonfly drone has been selected as the next New Frontiers mission, this time to Saturn’s moon Titan.  Animation of the vehicle taking off from the surface of the moon. (NASA)

A vehicle that flies like a drone and will try to unravel some of the mysteries of Saturn’s moon Titan was selected yesterday to be the next New Frontiers mission to explore the solar system.

Searching for the building blocks of life,  the Dragonfly mission will be able to fly multiple sorties to sample and examine sites around Saturn’s icy moon.

Titan has a thick atmosphere and features a variety of hydrocarbons, with rivers and lakes of methane, ethane and natural gas, as well as and precipitation cycles like on Earth.  As a result, Dragonfly has been described as an astrobiology mission because it will search for signs of the prebiotic environments like those on Earth that gave rise to life.

“Titan is unlike any other place in the solar system, and Dragonfly is like no other mission,” said Thomas Zurbuchen, NASA’s associate administrator for science at the agency headquarters in Washington.

“It’s remarkable to think of this rotorcraft flying miles and miles across the organic sand dunes of Saturn’s largest moon, exploring the processes that shape this extraordinary environment. Dragonfly will visit a world filled with a wide variety of organic compounds, which are the building blocks of life and could teach us about the origin of life itself.”

 

Saturn’s moon Titan is significantly larger than our moon, and larger than the planet Mercury. It features river channels of ethane and methane, and lakes of liquified natural gas. It is the only other celestial body in our solar system that has flowing liquid on its surface. (NASA)

As described in a NASA release, Titan is an analog to the very early Earth, and can provide clues to how life may have arisen on our planet.

Dragonfly will explore environments ranging from organic dunes to the floor of an impact crater where liquid water and complex organic materials key to life once existed together for possibly tens of thousands of years. Its instruments will study how far prebiotic chemistry may have progressed.

They also will investigate the moon’s atmospheric and surface properties and its subsurface ocean and liquid reservoirs. Additionally, instruments will search for chemical evidence of past or extant life.

Because it is so far from the sun, Titan’s surface temperature is around -290 degrees Fahrenheit and its surface pressure is 50 percent higher than Earth’s.… Read more

Methane on Mars. Here Today, Gone Tomorrow

June 24, 2019 / / 0 Comments

On the 2,440th Martian day at Gale Crater, the Curiosity rover detected a large spike in the presence of the gas methane. It was by far the largest plume detected by the rover, and parallels an earlier ground-based discovery of an even larger plume of the gas.  (NASA, JPL-Caltech, MSSS)

The presence — and absence — of methane gas on Mars has been both very intriguing and very confusing for years.  And news coming out last week and then on Monday adds to this scientific mystery.

To the great surprise of the Curiosity rover team, their Sample Analysis on Mars instrument sent back a measurement of 21 parts per billion of methane on Thursday — by far the highest measurement since the rover landed at Gale Crater.

As Paul Mahaffy, principal investigator of the instrument that made the measurement, described it yesterday at a large astrobiology conference in Seattle, “We were dumbfounded.”

And then a few days later, all the methane was gone.   Mahaffy, and NASA headquarters, reported that the readings went down quickly to below 1 part per billion.

These perplexing findings are especially important because methane could — and also could not — be a byproduct of biology.  On Earth, more than 90 percent of methane is produced via biology.  On Mars — at this point, nobody knows.  But the question has certainly gotten scientists’ attention.

The most recent finding of a return to low methane levels suggests that last week’s methane detection was one of the transient methane plumes that have been observed in the past. While Curiosity scientists have noted background levels rise and fall seasonally, they haven’t found a pattern in the occurrence of these transient plumes.

“The methane mystery continues,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’re more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.”

This image was taken by the left Navcam on the Curiosity Mars rover on June 18, 2019, the day when a methane plume was detected.  It shows part of “Teal Ridge,” which the rover has been studying within a region called the “clay-bearing unit.” (NASA/JPL-Caltech)

The nature and size of this most recent methane plume will, by chance, be the most widely observed so far.

That’s because the Mars Express orbiter happened to be performing spot tracking observations at the Gale Crater right around the time Curiosity detected the methane spike. … Read more

The Interiors of Exoplanets May Well Hold the Key to Their Habitability

June 23, 2019 / / 1 Comment

Scientists have had a working — and evolving — understanding of the interior of the Earth for only a century or so.  But determining whether a distant planet is truly habitable may require an understanding of its inner dynamics — which will for sure be a challenge to achieve. (Harvard-Smithsonian Center for Astrophysics)

The quest to find habitable — and perhaps inhabited — planets and moons beyond Earth focuses largely on their location in a solar system and the nature of its host star,  the eccentricity of its orbit, its size and rockiness, and the chemical composition of its atmosphere, assuming that it has one.

Astronomy, astrophysics, cosmochemistry and many other disciplines have made significant progress in characterizing at least some of the billions of exoplanets out there, although measuring the chemical makeup of atmospheres remains a immature field.

But what if these basic characteristics aren’t sufficient to answer necessary questions about whether a planet is habitable?  What if more information — and even more difficult to collect information — is needed?

That’s the position of many planetary scientists who argue that the dynamics of a planet’s interior are essential to understand its habitability.

With our existing capabilities, observing an exoplanet’s atmospheric composition will clearly be the first way to search for signatures of life elsewhere.   But four scientists at the Carnegie Institution of Science — Anat Shahar, Peter Driscoll, Alycia Weinberger, and George Cody — argued in a recent perspective article in Science that a true picture of planetary habitability must consider how a planet’s atmosphere is linked to and shaped by what’s happening in its interior.

They argue that on Earth, for instance, plate tectonics are crucial for maintaining a surface climate where life can fill every niche. And without the cycling of material between the planet’s surface and interior, the convection that drives the Earth’s magnetic field would not be possible and without a magnetic field, we would be bombarded by cosmic radiation.

What makes a planet potentially habitable and what are signs that it is not. This graphic from the Carnegie paper illustrates the differences (Shahar et al.)

 

“The perspective was our way to remind people that the only exoplanet observable right now is the atmosphere, but that the atmospheric composition is very much linked to planetary interiors and their evolution,” said lead author Shahar, who is trained in geological sciences. “If there is a hope to one day look for a biosignature, it is crucial we understand all the ways that interiors can influence the atmospheric composition so that the observations can then be better understood.”

“We need a better understanding of how a planet’s composition and interior influence its habitability, starting with Earth,” she said. 

… Read more

Exoplanets With Complex Life May Be Very Rare, Even in Their “Habitable Zones”

June 14, 2019 / / 1 Comment

The term “habitable zone” can be a misleading one, since it describes a limited number of conditions on a planet to make it hospitable to life. (NASA)

 

For years now, finding planets in the habitable zones of their host stars has been a global astrophysical quest and something of a holy grail.  That distance from a star where temperatures could allow H20 to remain liquid some of the time has been deemed the “Goldilocks” zone where life could potentially emerge and survive.

The term is valuable for sure, but many in the field worry that it can be as misleading or confusing as it is helpful.

Because while the habitable zone is a function of the physics and architecture of a solar system, so much more is needed to make a planet actually potentially habitable.  Does it have an atmosphere?  Does it have a magnetic field. Does it orbit on an elliptical path that takes it too far (and too close) to the sun?  Was it sterilized during the birth of the host star and orbiting planets?  What kind of star does it orbit, and how old and luminous is that star?

And then there’s the sometimes confused understanding that many habitable zones may well support complex, even technologically-advanced life.  They are, after all, habitable.

But as a new paper in the Astrophysical Journal makes clear, the likelihood of a habitable zone planet being able to support complex life — anything beyond a microbe — is significantly limited by the amount of toxic chemicals such as carbon monoxide and excesses of carbon dioxide.

Eddie Schwieterman, a NASA postdoc at the University of California, Riverside and lead author of the article, told me that the odds for complex life on most exoplanets in their habitable zones weren’t great.

“A rough estimate is between 10-20% of habitable zone planets are truly suitable for analogs to humans and animals.” he said. “Of course, being located in this part of the habitable zone isn’t enough by itself – you still need the build-up of oxygen via the evolution of oxygenic photosynthesis and certain planetary biogeochemical cycles.”

 

A rendering of the exoplanet Kepler 442 b, compared in size to  Earth.  Kepler 442 b was detected using the Kepler Space Telescope and is 0ne of a handful of planets found so far deemed to be most likely to be habitable. But it’s 1200 light-years away, so learning its secrets will be challenging.

… Read more

A Grand Global Competition to Name 100 ExoWorlds

June 7, 2019 / / 0 Comments

Within the framework of its 100th anniversary commemorations, the International Astronomical Union (IAU) is organising the IAU100 NameExoWorlds global competition that allows any country in the world to give a popular name to a selected exoplanet and its host star. Exoplanet rendering by IAU.

Four years ago, the International Astronomical Union organized a competition to give popular names to 14 stars and 31 exoplanets that orbit them.  The event encouraged 570,000 people to vote and the iconic planet 51 Pegasi b became “Dimidium, ” 55 Cancri b became “Galileo,” and (among others) Formalhaut b became “Dagon.”

It remains unclear how often those popular names are used in either scientific papers or writing about the papers.  But the idea of giving mythical names, names that describe something unique about the planet (or star)  or that nod to famous astronomer or iconic writers has caught on and the IAU has a new naming contest up and running.

This one is the IAU NameExoWorlds global campaign, and almost 100 nations have signed up to organize public national campaigns that will  give new names to a selected exoplanet and its host star.

“This exciting event invites everyone worldwide to think about their collective place in the universe, while stimulating creativity and global citizenship,” shared Debra Elmegreen, IAU President Elect. “The NameExoWorlds initiative reminds us that we are all together under one sky.”

From a large sample of well-studied, confirmed exoplanets and their host stars, the IAU NameExoWorlds Steering Committee assigned a star-planet system to each country, taking into account associations with the country and the visibility of the host star from most of the country.

The national campaigns will be carried out from June to November 2019 and, after final validation by that NameExoWorlds Steering Committee, the global results will be announced in December 2019. The winning names will be used freely in parallel with the existing technical scientific names.

The bulge of the Milky Way, as imaged by the Hubble Space Telescope. Our galaxy is inferred to have hundreds of billions of stars, and even more planets. (NASA, ESA, and T. Brown (STScI);

 

The naming contest flows from the well-established fact that exoplanets are everywhere — at least one around most stars, scientists have concluded.  Some 4,500 exoplanets have been identified so far, but this is but the beginning.  Astronomers are confident there are hundreds of billions of exoplanets — ranging from small and rocky like Earth to massive gas giants much larger than Jupiter — in our galaxy reaches into the many billions.… Read more

A Magical Solar Eclipse From 1900, Recovered and Instructive

May 31, 2019 / / 0 Comments

 

Sometimes relics from the past help put the present into better focus.

Recovered footage of a 1900 total eclipse of the sun — believed to be the first captured — has been scanned, restored and then reassembled and retimed frame by frame to create a memorable and kind of spooky look at early astronomy. The film was found at the Royal Astronomical Society in London, reconstructed by the British Film Institute and made public this week.

As explained in a release from the two societies, the film was taken by one Nevil Maskelyne, a British magician, card sharp, levitator and more turned pioneering filmmaker and astronomer.

The eclipse was captured during an expedition to North Carolina with the British Astronomical Association.  As the release explained, at the time magic, the paranormal and science often fit comfortably together, and the emerging film industry was a tool for all and an instigator of invention.

“It was not an easy feat to film,” the release reports. “Maskelyne had to make a special telescopic adapter for his camera to capture the event. ”

The North Carolina expedition was Maskelyne’s second attempt to film a solar eclipse, but the only one to have survived — though it was also considered lost for decades.  He also had traveled to India in 1898 to photograph the phenomenon and apparently succeeded, though his film can was said to be stolen on the way home.

 

Light curve of star as an exoplanet transits between it and an observing telescope.

 

Compelling on its own, the footage also conveniently provides an exaggerated and instructive example of the primary technique now used to discover distant exoplanets: the “transit” method invented a century after Maskelyne filmed his eclipse.

But unlike what occurs a full solar eclipse,  when the moon blots out the sun as viewed from Earth,  the transit method measures the light from a host star to determine whether it dips ever so slightly — a sign that a planet is blocking some of the star’s light.

There are, of course, no total eclipses from transiting exoplanets because the planets are so much smaller than the suns.  But you get the idea.

You perhaps also get the idea that there has long been a certain showmanship in the display of astronomical wonders.  Space agencies certainly understand that and — with some turning of the nobs to make astronomical phenomenon appear in ways our eyes can take them in most dramatically  — have created some of the most majestic and magical images of our times.… Read more

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