Breaking Down Exoplanet Stovepipes

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he search for life beyond our solar system requires unprecedented cooperation across scientific disciplines. NASA's NExSS collaboration includes those who study Earth as a life-bearing planet (lower right), those researching the diversity of solar system planets (left), and those on the new frontier, discovering worlds orbiting other stars in the galaxy (upper right). Credits: NASA
The search for life beyond our solar system requires unprecedented cooperation across scientific disciplines. NASA’s NExSS collaboration includes those who study Earth as a life-bearing planet (lower right), those researching the diversity of solar system planets (left), and those on the new frontier, discovering worlds orbiting other stars in the galaxy (upper right). (NASA)

That fields of science can benefit greatly from cross-fertilization with other disciplines is hardly a new idea.  We have, after all, long-standing formal disciplines such as biogeochemistry — a mash-up of many fields that has the potential to tell us more about the natural environment than any single approach.  Astrobiology in another field that inherently needs expertise and inputs from a myriad of disciplines, and the NASA Astrobiology Institute was founded (in 1998) to make sure that happened.

Until fairly recently, the world of exoplanet study was not especially interdisciplinary.  Astronomers and astrophysicists searched for distant planets and when they succeeded came away with some measures of planetary masses, their orbits, and sometimes their densities.  It was only in recent years, with the advent of a serious search for exoplanets with the potential to support life,  that it became apparent that chemists (astrochemists, that is), planetary and stellar scientists,  cloud specialists, geoscientists and more were needed at the table.

Universities were the first to create more wide-ranging exoplanet centers and studies, and by now there are a number of active sites here and abroad.  NASA formally weighed in one year ago with the creation of the Nexus for Exoplanet System Science (NExSS) — an initiative which brought together 17 university and research center teams with the goal of supercharging exoplanet studies, or at least to see if a formal, national network could produce otherwise unlikely collaborations and science.

That network is virtual, unpaid, and comes with no promises to the scientists.  Still, NASA leaders point to it as an important experiment, and some interesting collabortions, proposals and workshops have come out of it.

“A year is a very short time to judge an effort like this,” said Douglas Hudgins, program scientist for NASA’s Exoplanet Exploration Program, and one of the NASA people who helped NExSS come into being.

“Our attitude was to pull together a group of people, do our best to give them tool to work well together, let them have some time to get to know each other, and see what happens.  One year down the road, though, I think NExSS is developing and good ideas are coming out of it.”

Illustration of what a sunset might look like on a moon orbiting Kepler 47c and its two suns. (Softpedia)
Illustration of what a sunset might look like on a moon orbiting Kepler 47c and its two suns. (Softpedia)

 

One collaboration resulted in a “White Paper” on how laboratory work today can prepare researchers to better understand future exoplanet measurements coming from new generation missions. Led by NExSS member Jonathan Fortney of the University of Clalfornia, Santa Cruz, it was the result of discussions at the first NExSS meeting in Washington, and was expanded by others from the broader community.

Another NExSS collaboration between Steven Desch of Arizona State University and Jason Wright of Penn State led to a proposal to NASA to study a planet being pulled apart by the gravitational force a white dwarf star.  The interior of the disintegrating planet could potentially be analyzed as its parts scatter.

Leaders of NExSS say that other collaborations and proposals are in the works but are not ready for public discussion yet.

In addition, NExSS — along with the NASA Astrobiology Institute (NAI) and the National Science Foundation (NSF) — sponsored an unusual workshop this winter at Arizona State University focused on a novel way to looking at whether an exoplanet might support life.  Astrophysicists and geoscientists (some paertr of NExSS teams; some not) spent three days discussing and debating how the field might gather and use information about the formation, evolution and insides of exoplanets to determine whether they might be habitable.

One participant was Shawn Domogal-Goldman, a research space scientist at the Goddard Space Flight Center and a leader of the NExSS group.  He’s an expert in ancient earth as well the astrophysics of exoplanets, and his view is that the Earth provides 4.5 billion years of physical, chemical, climatic and biological dynamics  that need to be mined for useful insights about exoplanets.

When the workshop was over he said: “For me, and I think for others, we’ll look back at this meeting years from now and say to ourselves, ‘We were there at the beginning of something big.”

NExSS has two more workshops coming up, one on “Biosignatures” July 27 t0 29 in Seattle and another on stellar-exoplanet interactions in November.  Reflecting the broad reach of NExSS, the biosignatures program has additional sponsors include the NASA Astrobiology Institute (NAI), NASA’s Exoplanet Exploration Program (ExEP), and international partners, including the European Astrobiology Network Association (EANA) and Japan’s Earth-Life Science Institute (ELSI).

SA (2001) By looking for signs of life like we have on earth, we focus on trying to find the presence of oxygen, ozone, water, carbon dioxide, methane and nitrous oxide; indicating plant or bacterial life. Looking at the figure above, we can see how complex Earth’s spectra is compared to Mars or Venus. This is because of various factors that balance and control the elements needed for life as a whole. In the same way, we’re hoping to find life that strongly interacts with its atmosphere on a global scale.
By looking for signs of life, scientists focus on the potential presence of oxygen, ozone, water, carbon dioxide, methane and nitrous oxide, which could indicate plant or bacterial life. The figure above shows how complex Earth’s spectra is compared to Mars or Venus. This is a reflection of the intricate balance and control of elements needed to support life. The upcoming NExSS workshop will focus on what we know, and need to know, about what future missions and observations should be looking for in terms of exoplanet biosignatures. (ESA)

The initial idea for NExSS came from Mary Voytek, senior scientist for astrobiology in NASA’s Planetary Sciences Division.  Interdisciplinary collaboration and solutions are baked into the DNA of astrobiology, so it is not surprising that an interdisciplinary approach to exoplanets would come from that direction.  In addition, as the study of exoplanets increasingly becomes a search for possible life or biosignatures on those planets, it falls very much into the realm of astrobiology.

Mary Voytek, NASA senior scientist for astrobiology, xxxx.
Mary Voytek, NASA senior scientist for astrobiology, who initially proposed the idea that became the NExSS initiative.

Hudgins said that while this dynamic is well understood at NASA headquarters, the structure of the agency does not necessarily reflect the convergence.  Exoplanet studies are funded through the Division of Astrophysics while astrobiology is in the Planetary Sciences Division.

NExSS is a beginning effort to bring the overlapping fields closer together within the agency,  and more may be on the way.  Said Hudgins:  “We could very well see some evolution in how NASA approaches the problem, with more bridges between astrobiology and exoplanets.”

NExSS is led by Natalie Batalha of NASA’s Ames Research Center in Moffett Field, California; Dawn Gelino with NExScI, the NASA Exoplanet Science Institute at the California Institute of Technology in Pasadena; and Anthony Del Genio of NASA’s Goddard Institute for Space Studies in New York City.

All three see NExSS as an experiment and work in progress, with some promising accomplishments already.  And some clear challenges.

NASA's NExSS initiative seeks to bring together scientists from varied backgrounds to address questions of exoplanet research. The initiative consists of 17 teams that had applied for NASA grants under a variety of different programs, but organizers are looking to bring other scientists into the process as well. (NASA)
NASA’s NExSS initiative seeks to bring together scientists from varied backgrounds to address questions of exoplanet research. The initiative consists of 17 teams that had applied for NASA grants under a variety of different programs, but organizers are looking to bring other scientists into the process as well. (NASA)

 

Del Genio, for instance, described the complex dynamics involved in having a team like his own — climate modelers who have spent years understanding the workings of our planet — determine how their expertise can be useful in better understanding exoplanets.

These are some of his thoughts:

“This sounds great, but in practice it is very difficult to do for a number of reasons.  First, all the disciplines speak different languages. Jargon from one field has to be learned by people in another field, and unlike when I travel to Europe with a Berlitz phrase book, there is no Earth-to-Astrophysics translation guide to consult.

Tony del Genio, a veteran research scientists at NASA's Goddard Institute for Space Studies in Manhattan.
Tony Del Genio, a veteran research scientists at NASA’s Goddard Institute for Space Studies in Manhattan.

“Second, we don’t appreciate what the important questions are in each others’ fields, what the limitations of each field are, etc.  We have been trying to address these roadblocks in the first year by having roughly monthly webinars where different people present research that their team is doing.  But there are 17 teams, so this takes a while to do, and we are only part way through having all the teams present.

“Third, NExSS is a combination of teams that proposed to different NASA programs for funding, and we are a combination of big and small teams.  We are also a combination of teams in areas whose science is more mature, and teams in areas whose science is not yet very mature (and maybe if you asked all of us you’d get 10 different opinions on whose science is mature and whose isn’t).

What’s more, he wrote, he sees an inevitable imbalance between the astrophysics teams — which have been thinking about exoplanets for a long time — and teams from other disciplines that have mature models and theories for their own work but are now applying those tools to think about exoplanets for the first time.

But he sees these issues as challenges rather than show-stoppers, and expects to see important — and unpredictable — progress during the three-year life of the initiative.

Natalie Batalie said that she became involved with NExSS because “I wanted to help expedite the search for life on exoplanets.”

Natalie Batalha, project scientist for the Kepler mission and a leader of the NExSS initiative.
Natalie Batalha, project scientist for the Kepler mission and a leader of the NExSS initiative.

“Reaching this goal requires interdisciplinary thinking that’s been difficult to achieve given the divisional boundaries within NASA’s science mission directorate.  NExSS is an experiment to see if cooperation between the divisions can lead to cross-fertilization of ideas and a deeper understanding of planetary habitability.”

She said that in the last year, scientists working on planetary habitability both inside and outside of NExSS — and funded by different science divisions within NASA — have had numerous NExSS-sponsored opportunities to interact, learn from each other and begin collaborations.

The Fortney et al “White Paper” on experimental data gaps, for example, was conceived during one of these gatherings, as was the need for a biosignatures analysis group to support NASA’s Science & Technology Definition Teams studying the possible flagship missions of the future.

Dawn Gelino sees NExSS as an opportunity to speed the pace of addressing and answering open questions in the exoplanet field.  “As a community, we’re making progress towards answering some of them faster than others,” she wrote to me.

 Dawn Gelino, NExScI Science Affairs senior scientist and a leader of the NExSS initiative.
Dawn Gelino, NExScI Science Affairs senior scientist and a leader of the NExSS initiative.

“NExSS gives us an opportunity to look at all of these questions from many points of view.  Suddenly, a problem that a team of researchers has been stuck on has the potential to be solved quickly by learning from those in other disciplines who have dealt with similar problems. ”

Gelino said that NExSS is also working with various NASA study and analysis groups, the teams that come together to take on complicated questions and can later guide and sometimes define some of the science of a NASA mission. The discussion and conclusions from the upcoming Seattle biosignatures workshop, for instance, will be taken up by NASA’s Exoplanet Program Analysis Group (ExoPAG).

As a result, Gelino said, “NExSS scientists can share the knowledge gained from their interactions with earth scientists, heliophysicists, and planetary scientists, which broadens the knowledge of the community as a whole.”

In full disclosure, Many Worlds is funded by NExSS but represents only the views of the writer.

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The Search for Exoplanet Life Goes Broad and Deep

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The scientific lessons learned over the centuries about the geological, chemical and later biological dynamics of Earth are beginning to enter the discussion of exoplanets, and especially which might be conducive to life. This is an artist's view of the young Earth under bombardment by asteroids, one of many periods with conditions likely to have parallels in other solar systems. (NASA's Goddard Space Flight Center Conceptual Image Lab)
The scientific lessons learned over the centuries about the geological, chemical and later biological dynamics of Earth are beginning to enter the discussion of exoplanets, and especially which might be conducive to life. This is an artist’s view of the young Earth under bombardment by asteroids, one of many periods with conditions likely to have parallels in other solar systems. (NASA’s Goddard Space Flight Center Conceptual Image Lab)

I had the good fortune several years ago to spend many hours in meetings of the science teams for the Curiosity rover, listening in on discussions about what new results beamed back from Mars might mean about the planet’s formation, it’s early history, how it gained and lost an atmosphere, whether it was a place where live could begin and survive.  (A resounding ‘yes” to that last one.)

At the time, the lead of the science team was a geologist, Caltech’s John Grotzinger, and many people in the room had backgrounds in related fields like geochemistry and mineralogy, as well as climate modelers and specialists in atmospheres.  There were also planetary scientists, astrobiologists and space engineers, of course, but the geosciences loomed large, as they have for all Mars landing missions.

Until very recently, exoplanet research did not have much of that kind interdisciplinary reach, and certainly has not included many scientists who focus on the likes of vulcanism, plate tectonics and the effects of stars on planets.  Exoplanets has been largely the realm of astronomers and astrophysicists, with a sprinkling again of astrobiologists.

But as the field matures, as detecting exoplanets and inferring their orbits and size becomes an essential but by no means the sole focus of researchers, the range of scientific players in the room is starting to broaden.  It’s a process still in its early stages, but exoplanet breakthroughs already achieved, and the many more predicted for the future, are making it essential to bring in some new kinds of expertise.

A meeting reflecting and encouraging this reality was held last week at Arizona State University and brought together several dozen specialists in the geo-sciences with a similar number specializing in astronomy and exoplanet detection.  Sponsored by NASA’s Nexus for Exoplanet Systems Science (NExSS), NASA Astrobiology Institute (NAI) and the National Science Foundation,  it was a conscious effort to bring more scientists expert in the dynamics and evolution of our planet into the field of exoplanet study, while also introducing astronomers to the chemical and geological imperatives of the distant planets they are studying.

Twenty years after the detection of the first extra-solar planet around a star, the time seemed ripe for this coming together — especially if the organizing goal of the whole exoplanet endeavor is to search for signs of life beyond Earth.

 

Our vast body of knowledge about the formation, processes and evolution of Earth will become increasingly important in the exoplanet field as new generations of instruments make different and more precise kinds of measurements possible. Using Earth dynamics as a guide, those measurements will be made into models of what might be occurring on the exoplanets. The artist rendering of exoplanet Upsilon Andromedea g by Ron Howard.
Our vast body of knowledge about the formation, processes and evolution of Earth will become increasingly important in the exoplanet field as new generations of instruments make different and more precise kinds of measurements possible. Using Earth dynamics as a guide, those measurements will be made into models of what might be occurring on the exoplanets. The artist rendering of exoplanet Upsilon Andromedae g is by Ron Howard, Black Cat Studios.

Ariel Anbar, a biogeochemist at ASU, was one of the leaders of the meeting and the call for a broader exoplanet effort.

“The astronomical community has been pushing hard to make very difficult measurement, but they really haven’t been thinking much about the planetary context of what they’re finding.  And for geoscience, our people haven’t thought much about astronomical observations because they are so focused on Earth.”

“But this makes little sense because exoplanets open up a huge new field for geoscientists, and the astronomers absolutely need them to make the calls on what many of the measurements of the future actually mean.”

What’s more, the knowledge of researchers familiar with the dynamics of Earth will be essential when planet hunters and planet characterizers put together their wish lists for what kind of instruments are included in future telescopes and spectrographs.  For instance, a deep knowledge would be useful of the Earth’s carbon cycle, or what makes for a stable planetary climate, or what minerals and chemistry a habitable planet probably needs.

And then there are all the false positives and false negatives that could come with detections (or non-detections) of possible signatures of life.  The search for life beyond Earth has already had two highly-public and controversial seeming detections of extraterrestrial life — first by the Viking landers in the 1970s and the Mars meteorite ALH84001 in the mid 1990s.  The two are now considered inconclusive at best, and discredited at worst.

The risk of a similar, and even more complex, confusing and ultimately controversial, discovery of signs of life on an exoplanet are great.  The Arizona State workshop debated this issue at length.

President’s Professor at ASU’s School of Earth and Space Exploration and Department of Chemistry and Biochemistry.
Ariel Anbar, President’s Professor at ASU’s School of Earth and Space Exploration and School of Molecular Sciences. He hopes that the drive to understand exoplanets will push his field to develop a missing general theory for the evolution of Earth and Earth-like planets.

What they came away with was the understanding that while one or two measured biosignatures from a distant planet would be enormously exciting, a deeper understanding of the planet’s atmosphere, interior, chemical makeup and relationship to its host star are pretty much required to make a firm conclusion about biological vs non-biological origins.  (Here is a link to an introductory and cautionary tale to the workshop by another of its organizers, astrophysicist Steven Desch.)

And so the issues under debate were:  Does a planet need plate tectonics to be able to support life?  (Yes on Earth, perhaps elsewhere.) Would the detection of oxygen in an exoplanet atmosphere signify the presence of life? (Possibly, but not definitively.)  Does the chemical and mineral composition of a planet determine its ability to support life? (As far as we can tell, yes.)  Does photosynthesis inevitably lead to an oxygen atmosphere?  (It’s complicated.)

All these issues and many more serve to make the case that exoplanet science and Earth or planetary science need each other.

This is by no means an entirely new message — the Virtual Planetary Laboratory at the University of Washington has taken the approach for a decade from the standpoint of astronomy and the New Earths team of the NAI from a geological standing point.   But still, its urgency and proposed reach was  quite unusual.

It is also a reflection of both the success and direction of exoplanet science, because scientists have — or will have in the years ahead — the instruments and knowledge to learn more about an exoplanet than its location.  The James Webb Space Telescope is expected to provide much advanced ability to read the chemical compositions exoplanet atmospheres, as will a new generation of mammoth ground-based telescopes under construction and (scientists in the field fervently hope) a NASA flagship mission for the 2030s that would be able to directly image exoplanets with great precision.

But really, it’s when more and better measurements come in that the hard work begins.

Transmission spectrum of exoplanet MIT
Information about the make-up of exoplanets comes largely by studying the transmission spectra produced as the planet crosses in front of its star.  The spectra can identify some of the elements and compounds present around the exoplanet. Christine Naniloff/MIT, Julien De Wit.

 

Astrophysicist Steve Desch, for instance,  believes it is highly important to know what Earth-sized planets are like without life.  Starting with a biologically dead exoplanet in the Earth-sized ballpark, it would be possible to get a far better idea of the signatures of a similar planet with life.  But that’s a line of thinking that Earth scientists and geochemists are not, he said, used to addressing.  He felt the ASU workshop provided some consciousness-raising about the kinds of issues that are important to the exoplanet community, and to the Earth scientist, too.

Scientists from the geoscience side see similar limitations in the thinking of exoplanet astronomers.  Christy Till, a geologist and volcano specialist at ASU, said that at the close of the three-day workshop, she wasn’t at all sure that exoplanet scientists have been aware of just how complex the issue of “habitability” will be.

“Our field has learned over the decades that the solid interior of a planet is a big control on whether that planet can be habitable — along with the presence of volcanoes, the cycling elements like carbon and iron, and a relatively stable climate.  These issues were not widely discussed in terms of exoplanets, so I think we can help move the research further.”

Till is relatively new to thinking about exoplanets, brought into the field by the indisciplinary ASU (and NExSS/NAI) approach. But she said it has been most exciting to have the potential usefulness of her kind of knowledge expand on such a galactic scale.

Although the amount of detailed information about exoplanets is very limited, Till (and others) said what is and will be available can be used to create predictive models.  Absent the models that researchers can start building now, future information coming in could easily be misunderstood or simply missed.

ASU geologist and assistant professor Christy Till, a relatively new and enthusiastic member of the exoplanet community. (Abigail Wiebel)
ASU geologist and assistant professor Christy Till, a relatively new and enthusiastic member of the exoplanet community. (Abigail Wiebel)

While the usefulness of geosciences is being largely embraced in the exoplanet field, there are clear caveats.  If Earth becomes the model for what is needed for life in the cosmos, then is the field falling into a new version of the misguided Earth-centric view that long dominated astronomy and cosmology?

With that concern in mind, astronomer Drake Deming of the Harvard-Smithsonian Center for Astrophysics made the case for collecting potential biosignatures of all kinds.  Since we don’t know how potential life on another planet might have formed, we also may well be unaware of what kind of signatures it would put out.  ASU geochemist Everett Shock was similarly wary of relying too heavily on the Earth model when trying to understand planets that may seem similar but are inevitably different.

And Ariel Anbar felt challenged by his more complete realization post-workshop that the exoplanets available to study for the foreseeable feature will not be Earth-sized, but will be “Super-Earths” with radii up to 1.5 times as great as that of our planet.  A proponent of much greater exoplanet-geoscience collaboration, he said the Earth science community has a big job ahead figuring out how the processes and dynamics understood on Earth would actually apply on these significantly larger relatives.

One participant at the workshop pretty much personifies the interdisciplinary bridge under construction , and he was encouraged by the extensive back-and-forth between the space scientists and the Earth scientists.

Shawn Domogal-Goldman, a research space scientist at the Goddard Space Flight Center and a leader of the NExSS group, is an expert in ancient earth as well the astrophysics of exoplanet detection and characterizing.  His view is that the Earth provides 4.5 billion years of physical, chemical, climatic and biological dynamics  that need to be mined for useful insights about exoplanets.

“For me, and I think for others, we’ll look back at this meeting years from now and say to ourselves, ‘We were there at the beginning of something big.'”

 

 

 

 

 

 

 

 

 

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Shredding Exoplanets, And The Mysteries They May Unravel

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In this artist’s conception, a tiny rocky object vaporizes as it orbits a white dwarf star. Astronomers have detected the first planetary object transiting a white dwarf using data from the K2 mission. Slowly the object will disintegrate, leaving a dusting of metals on the surface of the star. (NASA)
In this artist’s conception, a small planet or planetesimal vaporizes as it orbits close to a white dwarf star. The detection of several of these disintegrating planets around a variety of stars has led some astronomers to propose intensive study of their ensuing dust clouds as a surprising new way to learn about the interiors of  exoplanet.  (NASA)

One of the seemingly quixotic goals of exoplanet scientists is to understand the chemical and geo-chemical compositions of the interiors of the distant planets they are finding.   Learning whether a planet is largely made up of silicon or magnesium or iron-based compounds is essential to some day determining how and where specific exoplanets were formed in their solar systems, which ones might have the compounds and minerals believed to be necessary for  life, and ultimately which might actually be hosting life.

Studying exoplanet interiors is a daunting challenge for sure, maybe even more difficult in principle than understanding the compositions of exoplanet atmospheres.  After all, there’s still a lot we don’t know about the make-up of planet interiors in our own solar system.

An intriguing pathway, however, has been proposed based on the recent discovery of exoplanets in the process of being shredded.  Generally orbiting very close to their suns, they appear to be disintegrating due to intense radiation and the forces of gravity.

And the result of their coming apart is that their interiors, or at least the dust clouds from their crusts and mantles, may well be on display and potentially measurable.

“We know very little for sure about these disintegrating planets, but they certainly seem to offer a real opportunity,” said Jason Wright, an astrophysicist at Pennsylvania State University with a specialty in stellar astrophysics.  No intensive study of the dusty innards of a distant, falling-apart exoplanet has been done so far,  he said, but in theory at least it seems to be possible.

Artist’s impression of disintegrating exoplanet KIC 12255 (C.U Keller, Leiden University)
Artist’s impression of disintegrating exoplanet KIC 12557548, the first of its kind ever detected. (C.U Keller, Leiden University)

And if successful, the approach could prove broadly useful since astronomers have already found at least four of disintegrating planets and predict that there are many more out there.  The prediction is based on, among other things, the relative speed with which the planets fall apart.  Since the disintegration has been determined to take only tens of thousands to a million years (a very short time in astronomical terms) then scientists conclude that the shreddings must be pretty common  –based on the number already caught in the act.

Saul Rappaport, professor emeritus of physics at MIT, led the team that first identified a disintegrating planet around KIC 12557548, using data from transit light curves collected by the Kepler Space Telescope.  The transits clearly did not indicate the usual small but detectable blockage by a solid body planet,  but were nonetheless intriguing because they were showing that something interesting was crossing (or occulting) the star and trailing an orbiting object.

Rappaport said he was definitely not searching for a dust trail from a disintegrating planet.

“Nobody had suggested that and we weren’t looking for it,” he said. “It took us completely by surprise.  Actually, after we found it, we spent many weeks trying to model it as a collection of solid bodies or something other than a disintegrating planet.  But ultimately we had to face up to what it is – occultation by dust emanating from a planet.”

Four years after his first paper was published, Rappaport said he is now 99 percent certain that KIC 12557548 is a close-in planet slowly disintegrating via the emission of dusty materials, as are three other similar objects subsequently detected.

Rappaport said that speaking generally, measurements of the size of the dust particles coming from those decaying planets would provide very valuable information to scientists, as would any insights into their chemical composition.  But he said that good data will be challenging to collect and equally difficult to interpret.

When an Earth-size planet passes in front of a star, it creates a symmetric dip in the star's light that's shaped like the red curve here. But astronomers detected the strange-looking, blue dip in light from the white dwarf 1145+017. The team suspects the signal comes from a tiny disintegrating planet or asteroid and its comet-like dusty tail. The black dots are measurements recorded by the Kepler spacecraft during its K2 mission. CfA / A. Vanderburg - See more at: http://www.skyandtelescope.com/astronomy-news/white-dwarf-eats-planet2610201523/#sthash.p9521Fxi.dpuf
When an Earth-size planet passes in front of a star, it creates a symmetric dip in the star’s light that’s shaped like the red curve here. But astronomers detected the strange-looking, blue dip in light from the white dwarf 1145+017. The team suspects the signal comes from a tiny disintegrating planet or asteroid and its comet-like dusty tail. (CfA /A. Vanderburg)

Unrelated to Rappaport’s work, Wright and a Penn State team, although with from the Arizona State University astrophysicist Steve Desch and others, have just sent a proposal into NASA to fund  disintegrating exoplanet research using ground-based telescopes and the Hubble Space Telescope.

The collaboration originated at a meeting of the Nexus for Exoplanet Systems Science (NExSS), a five-year NASA initiative to bring together exoplanet scientists from a variety of disciplines with the goal of having them work together across disciplines.  Organized by Mary Voytek, NASA’s senior scientist for astrobiology, it aims to bring the highly interdisciplinary model of astrobiology to the field of characterizing exoplanets.

“This is a project that really calls for, in fact requires, an interdisciplinary approach,” Desch said.  “This is where astronomy and astrophysics meet planetary science and geology, and that should be a very fruitful place.”

Is a measure of the interdisciplinary effort, their team also includes Casey Lisse at the Johns Hopkins University Applied Physics Laboratory.  He’s a comet scientist with a specialty in planet formation and astromineralogy.

Jason Wright, associate professor at Penn State University, initiated the collaboration to use disintegrating planets as a pathway to understanding exoplanet interiors. (Gudmundur Stefansson)
Jason Wright, associate professor at Penn State University, initiated the collaboration to use disintegrating planets as a pathway to understanding exoplanet interiors. (Gudmundur Stefansson)

Wright and Desch want to focus on the unusual transit signals from five stars — three M dwarf identified by Kepler, one a burned-out but super-dense white dwarf and other made famous last fall when a substantial and currently impossible-to-explain dust cloud was detected nearby it.  All the known explanations to explain it were deemed inadequate, which led to (last option) suggestions that perhaps it was an alien “megastructure” or Dyson swarm built by intelligent beings.

Wright was part of the group trying to explain the vast cloud around the star — KIC 8462852 or “Tabby’s star,” named after Yale University post-doc and co-founder Tabetha Boyajian) and now suspects that a disintegrating planet could be a source (though he says that Desch was the first to make the case.)

KIC 8462852, informally known as Tabby’s Star, is a magnitude +11.7 F-type main-sequence star located in the constellation Cygnus approximately 1,480 light-years from Earth. Data from NASA’s Kepler space telescope shows that the star displays aperiodic dimming of 20 percent and more. KIC 8462852 is shown here in infrared (2MASS survey, left) and ultraviolet (GALEX). Image credit: IPAC/NASA (infrared); STScI/NASA (ultraviolet).
KIC 8462852, informally known as Tabby’s Star, is a magnitude +11.7 F-type main-sequence star located in the constellation Cygnus approximately 1,480 light-years from Earth. Data from NASA’s Kepler space telescope shows that the star displays unexplained periodic dimming of 20 percent and more. KIC 8462852 is shown here in infrared (2MASS survey, left) and ultraviolet (GALEX) IPAC/NASA (infrared); STScI/NASA (ultraviolet)

The object that orbits a white dwarf star at a distance about the same as between Earth and the moon.  When its discovery was announced last year by Andrew Vanderburg of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, he said that something unique had been found:  “We’re watching a solar system get destroyed.”

The planet (or planetesimal) orbits its white dwarf, WD 1145+017, once every 4.5 hours. This orbital period places it extremely close to the super-dense star, and that speeds the shredding and evaporating of the planet. But makes it a theoretically easier target to observe.  Each time it orbits is a potentially detectable transit to be captured and studied.

White dwarf stars have also served as an earlier destination for those looking for information about potential insides of planets, but via a more indirect approach.  Because of their greatly heightened gravity, white dwarfs have surfaces covered only with light elements of helium and hydrogen. For years, researchers have found evidence that some white dwarf atmospheres are polluted with traces of heavier elements such as calcium, silicon, magnesium and iron. Scientists have long suspected that the source of this pollution has been asteroids or, what was then theoretical, a small planet being torn apart.

Steven Desch, an astrophysicist at ASU, sees a frequent gap between the work of astronomers and planetary scientists, and hopes to help bridge it.
Steve Desch, a theoretical astrophysicist at ASU, sees a frequent gap between in the exoplanet work of astronomers and of planetary scientists, and hopes to help bridge it. (ASU News)

Another prime target for disintegrating-planet research is the first one identified,  KIC 12557548 b.  Because it is so small — no bigger than Mercury — it’s an object that would never be detected by telescopes looking for transits across a star.  It is, after all, 1500 light years away.  But the dust cloud is much bigger and blocks as much as 1 percent of the light from the star every time it orbits.  To compare, our Jupiter would block about the same amount of the sun’s light in a similar scenario seen from afar.

The team leaders said that while their goal is to collect data that will help them understand the grain size and chemical composition of the dusty planetary remains, they also aim to refine the observing and spectrographic techniques for future observations — most especially on the James Webb Space Telescope.

The JWST, which launches in 2018, will have the capacity to collect information about the disintegrating planets that current instruments cannot.  But time on the telescope will be very costly and competitive, so Wright said the team will be doing the groundwork needed to make disintegrating planets an appealing subject for research.

“A lot of the observational technique has to be invented,” said Wright.  “JWST will be prime time for new science, but before that we need a lot of ground-based pre-study to make the case.”

The proposal also calls for extensive modeling of the dynamics of how dust grains would be released under the pressure of intense gravity and radiation pressure.

Coincidentally, a paper that models exoplanetary interiors authored by Li Zeng of the Harvard-Smithsonian Center for Astrophysics (CfA) and others, has been accepted for publication by The Astrophysical Journal.

Making sure it first could reproduce the Preliminary Reference Earth Model (PREM) — the standard model for Earth’s interior — Zeng and his team modified their planetary interior code to predict the structure of exoplanets with different masses and compositions, and applied it to six known rocky exoplanets with well-measured masses and radii.

They found that the other planets, despite their different masses and presumably different chemical makeup, nevertheless all appear to have a iron/nickel cores containing about 30% of the planet’s mass, very similar to the 32% of the Earth’s mass found in the Earth’s core. The remainder of each planet would be mantle and crust, just as with Earth.

The model, however, does not add new information about the observed make-up of exoplanet interiors.  That’s where the disintegration of close-in exoplanets just might come in.

In this Chandra image of ngc6388, researchers have found evidence that a white dwarf star may have ripped apart a planet as it came too close. When a star reaches its white dwarf stage, nearly all of the material from the star is packed inside a radius one hundredth that of the original star. Using several telescopes, including NASA’s Chandra X-ray Observatory, researchers have found evidence that a white dwarf star – the dense core of a star like the Sun that has run out of nuclear fuel – may have ripped apart a planet as it came too close. ( NASA)
In this Chandra image of globular cluster NGC 6388, researchers have found evidence that another white dwarf star may have ripped apart a planet as it came too close. When a star runs out of nuclear fuel and reaches its white dwarf stage, nearly all of its material from the star is packed inside a radius one hundredth that of the original star. The images was made with from images taken by several telescopes, including NASA’s Chandra X-ray Observatory. (NASA)
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Exoplanet Earth

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Snowball, or "slushball" Earths have occurred several times in Earth history, covering large swaths and perhaps at times all of the planet in glacial ice and snow. NSF
Snowball, or “slushball” Earths have occurred several times in our planet’s history, covering large swaths — and perhaps at times all of the planet — in glacial ice and snow. (NSF)

Some two billion years ago, all of Earth may well have been covered in snow and ice.  Oceans, continents, everything, and for many millions of years.  Observed from afar, the planet would be pretty low on the list of planets that might conceivably support life.  But we know that it did.

Five hundred to seven hundred million years ago, our planet had what scientists have determined to be another severe period of cold, with the global mean temperature somewhere around 10 degrees F.   Again, hardly a good candidate planet for life.  But in fact, the tropics were ice-free and Earth’s biosphere was preparing for its biggest explosion of life ever.

These kinds of insights and conclusions are part of the work now underway to use the earth and its climate history as a way to understand exoplanets, and some day to predict the best targets for examination.

cientific illustrations of recently discovered, potentially habitable worlds. Left to right: Kepler-22b, Kepler-69c, Kepler-62e, and Kepler-62f, compared with Earth at far right. (Credit: NASA/Ames/JPL-Caltech)
Illustrations of exoplanets that orbit their suns within a habitable zone. Left to right: Kepler-22b, Kepler-69c, Kepler-62e, and Kepler-62f, compared with Earth at far right. (NASA/Ames/JPL-Caltech)

It is a field with numerous players, but perhaps none so deeply engaged as NASA’s Goddard Institute for Space Studies (GISS) in New York City.

Using the same 3D modeling that it produces to understand our currently changing climate,  GISS and its collaborators is pushing further into the study of ancient Earth and solar system climates as a way to better understand exoplanets and someday identify potentially inhabited, or at least habitable, candidates.

Anthony Del Genio, a senior climate scientist at GISS, is the team leader for this novel effort, which includes some 30 scientists from a variety of institutions.

Anthony Del Genio, leader of GISS team using cutting edge Earth climate models to better understand conditions on exoplanets.
Anthony Del Genio, leader of GISS team using cutting edge Earth climate models to better understand conditions on exoplanets.

Undergirding the effort is the conviction that it would be a mistake to see exoplanets as static entities rather than as evolving bodies, with pasts and futures that can be as changeable as our own mutable planet.

“The beauty of Earth’s climate history for this project is that we have so many well studied fluctuations, and they give some tantalizing clues for a deeper understanding of other planets,”  said Del Genio, whose team is sponsored by both the NASA Planetary Atmospheres, Exobiology, and Habitable Worlds Programs  and the Nexus for Exoplanet System Science (NExSS,) a NASA initiative.  Both stress an interdisciplinary approach to big issues, and this team is on the cutting edge of that approach.

As Del Genio explains:  “Our planet started out uninhabitable and extremely hot.  Over many millions of years it cooled down and in time life started.  We know this happened when the atmosphere was still essentially without oxygen.

“Then both before and after the arrival of an oxygen atmosphere, the planet went into partial or potentially total snowball periods — millions of years when the Earth’s mean temperature was well below the freezing point.”  The Cambrian explosion of multi-cellular life followed the global freezing, and that in turn led some millions of years later to the warm and lush Cretaceous and its dinosaurs.

Many of these dramatic shifts involve climate, planetary and solar system dynamics that until recently played a limited role in exoplanet research.  But they do now.  The GISS Global Climate Model (GCM) is already made up of hundreds of thousands of lines of computer code, and now it will be expanded substantially to allow for the 3D visualization of exoplanet climates and planetary dynamics as well.  The potential power of the 3D exoplanet modeling is already apparent.

For instance, team member Linda Sohl used the GISS 3D model to see whether Earth circa 715 million years ago, with less carbon dioxide in the air, would be fully or partially covered in ice.  This was a time when the sun was some 6 percent fainter, scientists have calculated.  The model’s  attention-grabbing conclusion: large swaths of ocean were ice-free, despite a global mean temperature of just 9.9 degrees Fahrenheit.  So while global mean temperature is important, it does not alone determine the habitability of many planets.  Factors like the makeup of an atmosphere, how heat is dispersed and the tilt of the planet also play defining roles.

GCM model of “Slushball” Earth in a period when the mean global temperature was far below freezing but substantial parts of the oceans remained ice-free, illustrating how variable regional climates can be. (NASA, GISS-Columbia University)
GCM model of “Slushball” Earth in a period when the mean global temperature was far below freezing but substantial parts of the oceans remained ice-free, illustrating how variable regional climates can be. (NASA, GISS-Columbia University)

For exoplanet research, her team concluded, this means that the habitable zone around stars may well be larger than generally described, taking in planets that might have been written off as too cold (or too hot) before.  And since ice planets are of some considerable interest to astronomers because they shine so bright, this additional analysis (and others like it) could be quite useful in the years ahead.

“If we don’t know much about a planet, we don’t want to insert a lot of information into a model that we can’t validate.  But on Earth we know that the paleobiology called for a slushball Earth around 700 million years ago rather than a hardball, a very cold place but with much open ocean.  So the question is:  What climate, what atmospheres, what physical dynamics make that possible on Earth and other planets?”

She said that so far, astronomical models of exoplanets have been pretty straight-forward, looking at distance from the sun, how much light is being reflected, the path of the planet’s orbit.  But now the models can add atmospheres with differing chemical makeups,  different spin axes for the planets, different planet sizes, different classes of suns and gravity conditions. The researchers can run the 3D models and then see what conditions are produced, and especially can see if they produce a possibly habitable climate and world.

It’s a bounty of added dimensions, and it brings often separated scientific disciplines together. And, says Sohl, it provides a constant reminder of the “enormous range of possibilities driving the conditions we actually see.”

The models can be used to create (or simulate) endlessly variable planetary conditions.  What might happen, for instance, if an Earth-like planet rotated on its spin axis very slowly (a full rotation in 128 days rather than 24 hours?)  The model shows a potentially more lush, “superhabitable” planet.

 

 The example in the figure is for an otherwise Earth-like planet that rotates on its axis once every 128 days instead of once every 24 hours or so. It shows an "aridity index" that maps out the dry places (yellow-brown) and the wet places (green). The slowly rotating version of Earth has climate zones very different from actual Earth - the Sahara desert has turned into a rain forest, and the northern US and Canada have become more arid like Los Angeles, while Los Angeles has become rainier. Overall we find that if you slow down Earth's rotation, you make a planet that has more of its land area receiving enough rain to allow life to thrive and less of the "hyperarid" area in which life struggles. This is an example of the idea that there may be "superhabitable" planets out there

A computer generated “aridity index” that maps out the dry places (yellow-brown) and the wet places (green) of an Earth-like planet that rotates on its axis much more slowly than Earth. The slowly rotating version of Earth has climate zones very different from actual Earth – the Sahara desert has turned into a rain forest, and the northern U.S. and Canada have become more arid like Los Angeles. Overall, slowing the rotation produces a rocky planet with rain and possibly habitable conditions on more of the surface of the planet. (NASA GISS-Columbia University)

Or how about exploring a Venus from long ago that may have had oceans?  It is generally believed that Venus and Earth formed with similar compositions, but that Venus’ closer position to the Sun created a “runaway greenhouse” effect that caused it to lose all its water and become the hot, dry place we see today.  Lava from volcanic eruptions has covered most of the surface of Venus, and so the original features of “paleo-Venus” are in hiding.

The red areas in the figure are mostly ocean areas, with temperatures of about 25 degrees C, like a tropical resort (but very humid). The highland areas have temperatures just above freezing (yellow) or below freezing (blue) in the most mountainous parts. (NASA GISS-Columbia University)
The red areas in the figure are mostly ocean areas, with temperatures of about 25 degrees C, like a tropical resort (but very humid). The highland areas have temperatures just above freezing (yellow) or below freezing (blue) in the most mountainous parts. (NASA GISS-Columbia University)

But it does appear likely that Venus once did have a lot of water:  the Pioneer probe to Venus more than 30 years ago found that the deuterium-to-hydrogen ratio on that planet is higher than on Earth.  This means that there is a higher percentage of  “heavy hydrogen” to regular hydrogen, and that is generally interpreted to mean there was once a lot of water.

So GISS climate modeler Michael Way took a topographic map of Venus based on findings from another mission, filled in the lowlands with an ocean of water, and ran the global climate model to simulate the climate of ancient days on Venus.  The result was a planet with clouds that would block some of the sun’s rays and would produce a potentially habitable planet.

Del Genio and colleague Jeff Jonas also modeled a water-world exoplanet to see if it would be covered in clouds, as some had suggested.  The water-world possibility has generally been associated with “super-Earths” with a lot more mass and atmospheric pressure than Earth, so the Earth-based model has its limits.

But Del Genio said it addresses at least one question that the exoplanet community has had about water worlds – whether the surface of an all-ocean planet would be impossible to see because of cloud cover. “Our simulation shows that is not the case – the aqua-planet has mid-latitude frontal storms just like we do in the U.S. and big convective storms in two bands on either side of the equator. But it has lots of clear areas as well. That’s because clouds form where air rises and dissipate where air sinks.”

A water world on a rocky planet. The GCM model showed that it would not necessarily be entirely closed in by clouds. (NASA GISS-Columbia University)
A water world on a rocky planet. The GCM model showed that it would not necessarily be entirely closed in by clouds. (NASA GISS-Columbia University)

The GISS exoplanet project in many ways looks forward to the time when NASA has a powerful exoplanet direct imaging telescope in the sky, perhaps in the 2030s, or when the next generation of vastly enlarged ground-based telescopes have been built and commissioned.  Many researchers say that only with the ability to collect vastly more light than today from around the exoplanets will the most important details of their composition be revealed.

So a major part of the job of the exoplanet modeling team (and many other exoplanet scientists) is to prepare for that day.

“What we’re doing is trying to find the best places to point the telescopes, the most likely to support a habitable surface,” said Michael Way. “We’re helping to set the stage for discoveries coming 10, 20, 30 years from now.”

 

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The Exoplanet Era

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Many, and perhaps most stars have solar systems with numerous planets, as in this artist rendering of Kepler 11. (NASA)

Throughout the history of science, moments periodically arrive when new fields of knowledge and discovery just explode.

Cosmology was a kind of dream world until Edwin Hubble established that the universe was expanding, and doing so at an ever-faster rate. A far more vibrant and scientific discipline was born. On a more practical level, it was only three decades ago that rudimentary personal computers were still a novelty, and now computer-controlled, self-driving cars are just on the horizon. And not that long ago, genomics and the mapping of the human genome also went into hyperspeed, and turned the mysterious into the well known.

Most frequently, these bursts of scientific energy and progress are the result of technological innovation, coupled with the far-seeing (and often lonely and initially unsupported) labor and insights of men and women who are simply ahead of the curve.

We are at another of those scientific moments right now, and the subject is exoplanets – the billions (or is it billions of billions?) of planets orbiting stars other than our sun.

The 20th anniversary of the breakthrough discovery of the first exoplanet orbiting a sun, 51 Pegasi B, is being celebrated this month with appropriate fanfare. But while exoplanet discovery remains active and planet hunters increasingly skilled and inventive, it is no longer the edgiest frontier.

Now, astronomers, astrophysicists, astrobiologists, planetary scientists, climatologists, heliophysicists and many more are streaming into a field made so enticing, so seemingly fertile by that discovery of the apparent ubiquitiousness of exoplanets.

The new goal: Identifying the most compelling mysteries of some of those distant planets, and gradually but inexorably finding ever-more inventive ways to solve them. This is a thrilling task on its own, but the potential prize makes it into quite an historic quest. Because that prize is the identification of extraterrestrial life.

The presence of life beyond Earth is something that humans have dreamed about forever – with a seemingly intuitive sense that there just had to be other planets out there, and that it made equal sense that some of them supported life. Hollywood was on to this long ago, but now we have the beginning technology and fast-growing knowledge to transform that intuitive sense of life out there into a working science.

The thin gauzy rim of the planet in foreground is an illustration of its atmosphere. (NASA’s Goddard Space Flight Center)
The thin gauzy rim of the planet in foreground is an illustration of its atmosphere. (NASA’s Goddard Space Flight Center)

Already the masses and orbits of several thousand exoplanets have been measured. Some planets have been identified as rocky like Earth (as opposed to gaseous like Jupiter.) Some have been found in what the field calls “habitable zones” – regions around distant suns where liquid water could plausibly run on a surface –as it does on Earth and once did on Mars. And some exoplanets have even been determined to have specific compounds – carbon dioxide, water, methane, even oxygen – in their atmospheres.

This and more is what I will be exploring, describing, hopefully bringing to life through an on-going examination of this emerging field of science and the inventive scientists working to understand planets and solar systems many light-years away. Theirs is a daunting task for sure, and progress may be halting. But many scientists are convinced that the goal is entirely within reach – that based on discoveries already made, the essential dynamics and characteristics of very different kinds of planets and solar systems are knowable. Thus the name of this offering: “Many Worlds.”

Artist rendering of early stages of planet formation in the swirl and debris of the disk of a new star. (NASA/JPL-Caltech)
Artist rendering of early stages of planet formation in the swirl and debris of the disk of a new star. (NASA/JPL-Caltech)

I was first introduced to, and captivated by, this cosmic search in a class for space journalists taught by scientists including Sara Seager, a dynamic young professor of physics and planetary science at M.I.T., a subsequently-selected MacArthur “genius,” and a pioneer in the field not of discovering exoplanets, but of characterizing them and their atmospheres. And based on her theorizing and the observations of many others, she was convinced that this characterizing would lead to the discovery of very distant extraterrestrtial life, or at least to the discovery of planetary signatures that make the presence of life highly probable. Just this week, she predicted the discovery could take place within a decade.

It was in 2010 that she began her book “Exoplanet Atmospheres” with the statement: “A new era in planetary science is upon us.” I would take it further: A new era has arrived in the human drive to understand the universe and our place in it. Exoplanets and their solar systems are a magnet to young scientists, says Paul Hertz, the head of NASA’s Astrophysics Division. Almost a third of the papers presented at astronomy conferences these days involve exoplanets, he said, and “it’s hard to find scientists in our field under thirty not working on exoplanets.” Go to a major geology conference, or a planetary science meeting, and much the same will be true.

And why not? I think of this moment as akin to the time in the 17th century when early microscopes revealed a universe of life never before seen. So many new questions to ask, so many discoveries to make, so much exciting and ultimately world-changing science ahead.

But the challenge of characterizing exoplanets and some day identifying signs of life does not lend itself to the kind of solitary or small group work that characterized microbiology (think the breakthrough NASA Kepler mission and the large team needed to make it reality and to analyze its results.) Not only does it require costly observatories and telescopes and spectrometers, but it also needs the expertise that scientists from different fields can bring to the task – rather like the effort to map the human genome.

That is the organizing logic of astrobiology – the more general hunt for life elsewhere in our solar system and far beyond, alongside the search for clues into how life may have started on our planet. NASA is eager to encourage that same spirit in the more specific but nonetheless equally sprawling exploration of exoplanets, their atmospheres, their physical makeup, their climates, their suns, their neighborhoods.

The Earth alongside “Super-Earth-” sized exoplanets identified with the Kepler Space Telescope. (NASA Ames / JPL-Caltech)
The Earth alongside “Super-Earth-” sized exoplanets identified with the Kepler Space Telescope. (NASA Ames / JPL-Caltech)

The result was the creation this summer of the the Nexus for Exoplanet System Science (NExSS), a group that will be led by 17 teams of scientists from around the country already working on some aspect of the rich exoplanet opportunity. The group was selected from teams that had applied for grants from NASA’s Astrobiology Institute, an arm of its larger NASA Astrobiology Program, as well as other NASA programs in the Planetary Sciences, Astrophysics and Astronomy divisions.

Their mandate is to spark new approaches in the effort to understand exoplanets by identifying areas without consensus in the broader community, and then fostering collaborations here and abroad to address those issues. “Many Worlds” grew out of the NExSS initiative, and will chronicle and explain the efforts of some team members as they explore how exo-plants and exo-creatures might be detected; what can be learned from afar about the surfaces and cores of exoplanets and how both play into the possibility of faraway life; the presence and dynamics of exo-weather, what we can learn about exoplanets from our own planet and solar system, and so much more.

A few of the teams are small, but many are quite large, established and mature – perhaps most especially the Virtual Planetary Laboratory at the University of Washington, and run by Victoria Meadows. Since 2001, the virtual lab has collaborated with researchers representing many disciplines, and from as many as 20 institutions, to understand what factors might best predict whether an exoplanet harbors life, using Earth as a model.

But just as I will be venturing beyond NExSS in my writing about this new era of exploration, so too will NExSS be open to the involvement of other scientists in the field. The original group has been tasked with identifying an agenda of sorts for NASA exoplanet missions and efforts ahead. But its aim is to be inclusive and its conclusions and recommendations will only be as useful and important as the exoplanet community writ large determines them to be.

The Carina Nebula, one of many regions where stars come together and planets later form made out of the surrounding dust, gas and later rock. (NASA, ESA, and the Hubble SM4 ERO Team)
The Carina Nebula, one of many regions where stars come together and planets later form made out of the surrounding dust, gas and later rock. (NASA, ESA, and the Hubble SM4 ERO Team)

This is a moment pregnant with promise. Systematically investigating exoplanets and their environs is an engine for discovery and a pathway into that largest question of whether or not we are alone in the universe.

Will scientists some day find worlds where donkeys talk and pigs can fly (as at least one “everything is possible” philosopher has posited)? Unlikely.

But just as microscopes and the scientists using them led to the science of microbiology and most of modern medicine, so too are our orbiting observatories, Earth-based telescopes and the scientists who analyze their results are regularly opening up a world of myriad and often surprising marvels.

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