Tag: NExSS (page 1 of 2)

A National Strategy for Finding and Understanding Exoplanets (and Possibly Extraterrestrial Life)

The National Academies of Science, Engineering and Medicine took an in-depth look at what NASA, the astronomy community and the nation need to grow the burgeoning science of exoplanets — planets outside our solar system that orbit a star. (NAS)

 

An extensive, congressionally-directed study of what NASA needs to effectively learn how exoplanets form and whether some may support life was released today, and it calls for major investments in next-generation space and ground telescopes.  It also calls for the adoption of an increasingly multidisciplinary approach for addressing the innumerable questions that remain unanswered.

While the recommendations were many, the top line calls were for a sophisticated new space-based telescope for the 2030s that could directly image exoplanets, for approval and funding of the long-delayed and debated WFIRST space telescope, and for the National Science Foundation and to help fund two of the very large ground-based telescopes now under development.

The study of exoplanets has seen remarkable discoveries in the past two decades.  But the in-depth study from the private, non-profit National Academies of Sciences, Engineering and Medicine concludes that there is much more that we don’t understand than that we do, that our understandings are “substantially incomplete.”

So the two overarching goals for future exoplanet science are described as these:

 

  • To understand the formation and evolution of planetary systems as products of star formation and characterize the diversity of their architectures, composition, and environments.
  • To learn enough about exoplanets to identify potentially habitable environments and search for scientific evidence of life on worlds orbiting other stars.

 

Given the challenge, significance and complexity of these science goals, it’s no wonder that young researchers are flocking to the many fields included in exoplanet science.  And reflecting that, it is perhaps no surprise that the NAS survey of key scientific questions, goals, techniques, instruments and opportunities runs over 200 pages. (A webcast of a 1:00 pm NAS talk on the report can be accessed here.)

 


Artist’s concept showing a young sun-like star surrounded by a planet-forming disk of gas and dust.
(NASA/JPL-Caltech/T. Pyle)

These ambitious goals and recommendations will now be forwarded to the arm of the National Academies putting together 2020 Astronomy and Astrophysics Decadal Survey — a community-informed blueprint of priorities that NASA usually follows.

This priority-setting is probably most crucial for the two exoplanet direct imaging missions now being studied as possible Great Observatories for the 2030s — the paradigm-changing space telescopes NASA has launched almost every decade since the 1970s.

Read more “A National Strategy for Finding and Understanding Exoplanets (and Possibly Extraterrestrial Life)”

False Positives, False Negatives; The World of Distant Biosignatures Attracts and Confounds

This artist’s illustration shows two Earth-sized planets, TRAPPIST-1b and TRAPPIST-1c, passing in front of their parent red dwarf star, which is much smaller and cooler than our sun. NASA’s Hubble Space Telescope looked for signs of atmospheres around these planets. (NASA/ESA/STScI/J. de Wit, MIT)

What observations, or groups of observations, would tell exoplanet scientists that life might be present on a particular distant planet?

The most often discussed biosignature is oxygen, the product of life on Earth.  But while oxygen remains central to the search for biosignatures afar, there are some serious problems with relying on that molecule.

It can, for one, be produced without biology, although on Earth biology is the major source.  Conditions on other planets, however, might be different, producing lots of oxygen without life.

And then there’s the troubling reality that for most of the time there has been life on Earth, there would not have been enough oxygen produced to register as a biosignature.  So oxygen brings with it the danger of both a false positive and a false negative.

Wading through the long list of potential other biosignatures is rather like walking along a very wet path and having your boots regularly pulled off as they get captured by the mud.  Many possibilities can be put forward, but all seem to contain absolutely confounding problems.

With this reality in mind, a group of several dozen very interdisciplinary scientists came together more than a year ago in an effort to catalogue the many possible biosignatures that have been put forward and then to describe the pros and the cons of each.

“We believe this kind of effort is essential and needs to be done now,” said Edward Schwieterman, an astronomy and astrobiology researcher at the University of California, Riverside (UCR).

“Not because we have the technology now to identify these possible biosignatures light years away, but because the space and ground-based telescopes of the future need to be designed so they can identify them. ”

“It’s part of what may turn out to be a very long road to learning whether or not we are alone in the universe”.

 

Artistic representations of some of the exoplanets detected so far with the greatest potential to support liquid surface water, based on their size and orbit.  All of them are larger than Earth and their composition and habitability remains unclear. They are ranked here from closest to farthest from Earth. 

Read more “False Positives, False Negatives; The World of Distant Biosignatures Attracts and Confounds”

Putting Together a Community Strategy To Search for Extraterrestrial Life

I regret that the formatting of this column was askew earlier; I hope it didn’t make reading too difficult.  But now those problems are fixed.

The scientific search underway for life beyond Earth requires input from many disciplines and fields. Strategies forward have to hear and take in what scientists in those many fields have to say. (NASA)

Behind the front page space science discoveries that tell us about the intricacies and wonders of our world are generally years of technical and intellectual development, years of planning and refining, years of problem-defining and problem-solving.  And before all this, there also years of brainstorming, analysis and strategizing about which science goals should have the highest priorities and which might be most attainable.

That latter process is underway now in regarding the search for life in the solar system and beyond, with numerous teams of scientists tackling specific areas of interest and concern and turning their group discussions into white papers.  In this case, the white papers will then go on to the National Academy of Sciences for a blue-ribbon panel review and ultimately recommendations on which subjects are exciting and mature enough for inclusion in a decadal survey and possible funding.

This is a generally little-known part of the process that results in discoveries, but scientists certainly understand how they are essential.  That’s why hundreds of scientists contribute their ideas and time — often unpaid — to help put together these foundational documents.

With its call for extraterrestrial habitability white papers, the NAS got more than 20 diverse and often deeply thought out offerings.  The papers will be studied now by an ad hoc, blue ribbon committee of scientists selected by the NAS, which will have the first of two public meetings in Irvine, Calif. on Jan. 16-18.

Shawn Domagal-Goldman, a leader of many NASA study projects and a astrobiologist at NASA’s Goddard Space Fight Center. (NASA)

Then their recommendations go up further to the decadal survey teams that will set formal NASA priorities for the field of astronomy and astrophysics and planetary science.  This community-based process that has worked well for many scientific disciplines since they began in the late 1950s.

I’m particularly familiar with two of these white paper processes — one produced at the Earth-Life Science Institute (ELSI) in Tokyo and the other with NASA’s Nexus for Exoplanet System Science (NExSS.)  What they have to say is most interesting.Read more “Putting Together a Community Strategy To Search for Extraterrestrial Life”

Can You Overwater a Planet?

Water worlds, especially if they have no land on them, are unlikely to be home to life, or at least lifewe can detect.  Some of the basic atmospheric and mineral cycles that make a planet habitable will be absent. Cool animation of such a world. (NASA)

Wherever we find water on Earth, we find life. It is a connection that extends to the most inhospitable locations, such as the acidic pools of Yellowstone, the black smokers on the ocean floor or the cracks in frozen glaciers. This intimate relationship led to the NASA maxim, “Follow the Water”, when searching for life on other planets.

Yet it turns out you can have too much of a good thing. In the November NExSS Habitable Worlds workshop in Wyoming, researchers discussed what would happen if you over-watered a planet. The conclusions were grim.

Despite oceans covering over 70% of our planet’s surface, the Earth is relatively water-poor, with water only making up approximately 0.1% of the Earth’s mass. This deficit is due to our location in the Solar System, which was too warm to incorporate frozen ices into the forming Earth. Instead, it is widely — though not exclusively — theorized that the Earth formed dry and water was later delivered by impacts from icy meteorites. It is a theory that two asteroid missions, NASA’s OSIRIS-REx and JAXA’s Hayabusa2, will test when they reach their destinations next year.

But not all planets orbit where they were formed. Around other stars, planets frequently show evidence of having migrated to their present orbit from a birth location elsewhere in the planetary system.

One example are the seven planets orbiting the star, TRAPPIST-1. Discovered in February this year, these Earth-sized worlds orbit in resonance, meaning that their orbital times are nearly exact integer ratios. Such a pattern is thought to occur in systems of planets that formed further away from the star and migrated inwards.

 

Trappist-1 and some of its seven orbiting planets.  They would have been sterilized by high levels of radiation in the early eons of that solar system — unless they were formed far out and then migrated in.  That scenario would also allow for the planets to contain substantial amounts of water. (NASA)

The TRAPPIST-1 worlds currently orbit in a temperate region where the levels of radiation from the star are similar to that received by our terrestrial worlds.… Read more “Can You Overwater a Planet?”

Getting Real About the Oxygen Biosignature

Oxygen, which makes up about 21 percent of the Earth atmosphere, has been embraced as the best biosignature for life on faraway exoplanets. New research shows that detecting distant life via the oxygen biosignature is not so straight-forward, though it probably remains the best show we have. (NASA)

 

I remember the first time I heard about the atmospheres of distant exoplanets and how could and would let us know whether life was present below.

The key was oxygen or its light-modified form, ozone.  Because both oxygen and ozone molecules bond so quickly with other molecules — think rust or iron oxide on Mars, silicon dioxide in the Earth’s crust — it was said that oxygen could only be present in large and detectable quantities if there was a steady and massive source of free oxygen on the planet.

On Earth, this of course is the work of photosynthesizers such as planets, algae and cyanobacteria, which produce oxygen as a byproduct.  No other abiotic, or non-biological, ways were known at the time to produce substantial amounts of atmospheric oxygen, so it seemed that an oxygen signal from afar would be a pretty sure sign of life.

But with the fast growth of the field of exoplanet atmospheres and the very real possibility of having technology available in the years ahead that could measure the components of those atmospheres, scientists have been busy modelling exoplanet formations, chemistry and their atmospheres.

One important goal has been to search for non-biological ways to produce large enough amounts of atmospheric oxygen that might fool us into thinking that life has been found below.

And in recent years, scientists have succeeded in poking holes in the atmospheric oxygen-means-life scenario.

Oxygen bonds quickly with many other molecules. That means has to be resupplied regularly to be present as O2 in an atmosphere . On Earth, O is mostly a product of biology, but elsewhere it might be result of non-biological processes. Here is an image of oxygen bubbles in water.

Especially researchers at the University of Washington’s Virtual Planetary Laboratory (VPL) have come up with numerous ways that exoplanets atmospheres can be filled (and constantly refilled) with oxygen that was never part of plant or algal or bacteria photo-chemistry.

In other words, they found potential false positives for atmospheric oxygen as a biosignature, to the dismay of many exoplanet scientists.

In part because she and her own team were involved in some of these oxygen false-positive papers, VPL director Victoria Meadows set out to review, analyze and come to some conclusions about what had become the oxygen-biosignature problem.… Read more “Getting Real About the Oxygen Biosignature”

The Very Influential Natalie Batalha

Natalie Batalha, project scientist for the Kepler mission and a leader of NASA’s NExSS initiative on exoplanets, was just selected as one of Time Magazine’s 100 most influential people in the world. (NASA, TIME Magazine.)

I’d like to make a slight detour and talk not about the science of exoplanets and astrobiology, but rather a particular exoplanet scientist who I’ve had the pleasure to work with.

The scientist is Natalie Batalha, who has been lead scientist for NASA’s landmark Kepler Space Telescope mission since soon after it launched in 2009, has serves on numerous top NASA panels and boards, and who is one of the scientists who guides the direction of this Many Worlds column.

Last week, Batalha was named by TIME Magazine as one of the 100 most influential people in the world. This is a subjective (non-scientific) calculation for sure, but it nonetheless seems appropriate to me and to doubtless many others.

Batalha and the Kepler team have identified more than 2500 exoplanets in one small section of the distant sky, with several thousand more candidates awaiting confirmation.  Their work has once and for all nailed the fact that there are billions and billions of exoplanets out there.

“NASA is incredibly proud of Natalie,” said Paul Hertz, astrophysics division director at NASA headquarters, after the Time selection was announced.

“Her leadership on the Kepler mission and the study of exoplanets is helping to shape the quest to discover habitable exoplanets and search for life beyond the solar system. It’s wonderful to see her recognized for the influence she has had on the world – and on the way we see ourselves in the universe.”

And William Borucki, who had the initial idea for the Kepler mission and worked for decades to get it approved and then to manage it, had this to say about Batalha:

“She has made major contributions to the Kepler Mission throughout its development and operation. Natalie’s collaborative leadership style, and expert knowledge of the population of exoplanets in the galaxy, will provide guidance for the development of successor missions that will tell us more about the habitability of the planets orbiting nearby stars.”

Batalha has led the science mission of the Kepler Space Telescope since it launched in 2009. (NASA)

As a sign of the perceived importance of exoplanet research, two of the other TIME influential 100 are discoverers of specific new worlds.  They are Guillem Anglada-Escudé (who led a team that detected a planet orbiting Proxima Centauri) and Michael Gillon (whose team identified the potentially habitable planets around the Trappist-1 system.)

But Batalha, and no doubt the other two scientists, stress that they are part of a team and that the work they do is inherently collaborative.… Read more “The Very Influential Natalie Batalha”

Ocean Worlds: Enceladus Looks Increasingly Habitable, and Europa’s Ocean Under the Ice More Accessible to Sample

NASA’s Cassini spacecraft completed its deepest-ever dive through the icy plume of Enceladus on Oct. 28, 2015. (NASA/JPL-Caltech)

It wasn’t that long ago that Enceladus, one of 53 moons of Saturn, was viewed as a kind of ho-hum object of no great importance.  It was clearly frozen and situated in a magnetic field maelstrom caused by the giant planet nearby and those saturnine rings.

That view was significantly modified in 2005 when scientists first detected signs of the icy plumes coming out of the bottom of the planet.  What followed was the discovery of warm fractures (the tiger stripes) near the moon’s south pole, numerous flybys and fly-throughs with the spacecraft Cassini, and by 2015 the announcement that the moon had a global ocean under its ice.

Now the Enceladus story has taken another decisive turn with the announcement that measurements taken during Cassini’s final fly-through captured the presence of molecular hydrogen.

To planetary and Earth scientists, that particular hydrogen presence quite clearly means that the water shooting out from Enceladus is coming from an interaction between water and warmed rock minerals at the bottom of the moon’s ocean– and possibly from within hydrothermal vents.

These chimney-like hydrothermal vents at the bottom of our oceans — coupled with a chemical mixture of elements and compounds similar to what has been detected in the plumes — are known on Earth as prime breeding grounds for life.  One important reason why is that the hydrogen and hydrogen compounds produced in these settings are a source of energy, or food, for microbes.

A logical conclusion of these findings:  the odds that Enceladus harbors forms of simple life have increased significantly.

To be clear, this is no discovery of extraterrestrial life. But it is an important step in the astrobiological quest to find life beyond Earth.

“The key here is that Enceladus can produce fuel that could be used by biology,” said Mary Voytek, NASA’s senior scientist for astrobiology, referring to the detection of hydrogen.

 

This graphic illustrates how scientists on NASA’s Cassini mission think water interacts with rock at the bottom of the ocean of Saturn’s icy moon Enceladus, producing hydrogen gas (H2). It remains unclear whether the interactions are taking place in hydrothermal vents or more diffusely across the ocean. (NASA)

“So now on this moon we have many of the components associated with life — water, a source of energy and many of the important chemical building blocks. … Read more “Ocean Worlds: Enceladus Looks Increasingly Habitable, and Europa’s Ocean Under the Ice More Accessible to Sample”

A Four Planet System in Orbit, Directly Imaged and Remarkable

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The era of directly imaging exoplanets has only just begun, but the science and viewing pleasures to come are appealingly apparent.

This evocative movie of four planets more massive than Jupiter orbiting the young star HR 8799 is a composite of sorts, including images taken over seven years at the W.M. Keck observatory in Hawaii.

The movie clearly doesn’t show full orbits, which will take many more years to collect. The closest-in planet circles the star in around 40 years; the furthest takes more than 400 years.

But as described by Jason Wang,  an astronomy graduate student at the University of California, Berkeley, researchers think that the four planets may well be in resonance with each other.

In this case it’s a one-two-four-eight resonance, meaning that each planet has an orbital period in nearly precise ratio with the others in the system.

The black circle in the center of the image is part of the observing and analyzing effort to block the blinding light of the star, and thus make the planets visible.

The images were initially captured by a team of astronomers including Christian Marois of the National Research Council of Canada’s Herzberg Institute of Astrophysics, who analyzed the data.  The movie animation was put together by Wang, who is part of the Berkeley arm of the Nexus for Exoplanet System Science (NExSS), a NASA-sponsored group formed to encourage interdisciplinary exoplanet science.

The star HR 8799 has already played a pioneering role in the evolution of direct imaging of exoplanets.  In 2008, the Marois group announced discovery of three of the four HR 8799 planets using direct imaging for the first time. On the same day that a different team announced the direct imaging of a planet orbiting the star Fomalhaut.

 


This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging. (NASA, ESA, and P. Kalas, University of California, Berkeley and SETI Institute)

HR 8799 is 129 light years away in the constellation of Pegasus.  By coincidence, it is quite close to the star 51 Pegasi, where the first exoplanet was detected in 1995.  It is less than 60 million years old, Wang said, and is almost five times brighter than the sun.

Wang said that the animation is based on eight observations of the planets since 2009.  He then used a motion interpolation algorithm to draw the orbit between those points.… Read more “A Four Planet System in Orbit, Directly Imaged and Remarkable”

The Stellar Side of The Exoplanet Story

K2-33b, shown in this illustration, is one of the youngest exoplanets detected to date. It makes a complete orbit around its star in about five days. Credits: NASA/JPL-Caltech

K2-33b, shown in this illustration, is one of the youngest exoplanets detected to date. It makes a complete orbit around its star in about five days, and as a result its characteristics are very much determined by its host. (NASA/JPL-Caltech)

 

When it comes to the study of exoplanets, it’s common knowledge that the host stars don’t get much respect.

Yes, everyone knows that there wouldn’t be exoplanets without stars, and that they serve as the essential background for exoplanet transit observations and as the wobbling object that allows for radial velocity measurements that lead to new exoplanets discoveries.

But stars in general have been seen and studied for ever, while the first exoplanet was identified only 20-plus years ago.  So it’s inevitable that host stars have generally take a back seat to the compelling newly-found exoplanets that orbit them.

As the field of exoplanet studies moves forward, however, and tries to answer questions about the characteristics of the planets and their odds of being habitable, the perceived importance of the host stars is on the rise.

The logic:  Stars control space weather, and those conditions produce a space climate that is conducive or not so conducive to habitability and life.

Space weather consists of a variety of enormously energetic events ranging from solar wind to solar flares and coronal mass ejections, and their characteristics are defined by the size, variety and age of the star.  It is often said that an exoplanet lies in a “habitable zone” if it can support some liquid water on its surface, but absent some protection from space weather it will surely be habitable in name only.

A recognition of this missing (or at least less well explored) side of the exoplanet story led to the convening of a workshop this week in New Orleans on “The Impact of Exoplanetary Space Weather On Climate and Habitability.”

“We’re really just starting to detect and understand the secret lives of stars,”  said Vladimir Airapetian, a senior scientist at the Goddard Space Flight Center.  He organized the highly interdisciplinary workshop for the Nexus for Exoplanet Space Studies (NExSS,) a NASA initiative.

“What has become clear is that a star affects and actually defines the character of a planet orbiting around it,” he said.  “And now we want to look at that from the point of view of astrophysicists, heliophysicists, planetary scientists and astrobiologists.”

William Moore, principal investigator for a NASA-funded team also studying how host stars affect their exoplanets, said the field was changing fast and that “trying to understand those (space weather) impacts has become an essential task in the search for habitable planets.”

 The newly discovered giant planet orbits around its young and active host star inside the inner hole of a dusty circumstellar disk (artist view). Credit: Max Planck Institute for Astronomy. The newly discovered giant planet orbits around its young and active host star inside the inner hole of a dusty circumstellar disk (artist view). Credit: Max Planck Institute for Astronomy.

The newly discovered giant planet orbits around its young and active host star inside the inner hole of a dusty circumstellar disk (artist view).

Read more “The Stellar Side of The Exoplanet Story”

One Planet, But Many Different Earths

Artist conception of early Earth. (NASA/JPL-Caltech)

Artist conception of early Earth. (NASA/JPL-Caltech)

We all know that life has not been found so far on any planet beyond Earth — at least not yet.  This lack of discovery of extraterrestrial life has long been used as a knock on the field of astrobiology and has sometimes been put forward as a measure of Earth’s uniqueness.

But the more recent explosion in exoplanet discoveries and the next-stage efforts to characterize their atmospheres and determine their habitability has led to rethinking about how to understand the lessons of life of Earth.

Because when seen from the perspective of scientists working to understand what might constitute an exoplanet that can sustain life,  Earth is a frequent model but hardly a stationary or singular one.  Rather, our 4.5 billion year history — and especially the almost four billion years when life is believed to have been present  — tells many different stories.

For example, our atmosphere is now oxygen-rich, but for billions of years had very little of that compound most associated with complex life.  And yet life existed.

The same with temperature.  Earth went through snowball or slushball periods when most of the planet’s surface was frozen over.  Hardly a good candidate for life, and yet the planet remained habitable and inhabited.

And in its early days, Earth had a very weak magnetic field and was receiving only 70 to 80 percent as much energy from the sun as it does today.  Yet it supported life.

“It’s often said that there’s an N of one in terms of life detected in the universe,” that there is but one example, said Timothy Lyons, a biogeochemist and distinguished professor at University of California, Riverside.

“But when you look at the conditions on Earth over billion of years, it’s pretty clear that the planet had very different kinds of atmospheres and oceans, very different climate regimes, very different luminosity coming from the sun.  Yet we know there was life under all those very different conditions.

“It’s one planet, but it’s silly to think of it as one planetary regime. Each of our past chapters is a potential exoplanet.”

 

A rendering of the theorized "Snowball Earth" period when, for millions of years, the Earth was entirely or largely covered by ice, stretching from the poles to the tropics. This freezing happened over 650 million years ago in the Pre-Cambrian, though it's now thought that there may have been more than one of these global glaciations. They varied in duration and extent but during a full-on snowball event, life could only cling on in ice-free refuges, or where sunlight managed to penetrate through the ice to allow photosynthesis.

A particularly extreme phase of our planet’s history is called  the “Snowball Earth” period.  During these episodes, the Earth’s surface was entirely or largely covered by ice for millions of years, stretching from the poles to the tropics. One such freezing happened over 700 to 800 million years ago in the Pre-Cambrian, around the time that animals appeared.

Read more “One Planet, But Many Different Earths”
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