From campus to wherever you call home, we welcome you to learn from and connect with the College of Arts & Sciences community through public events spanning the arts, humanities, natural sciences, and social sciences. We hope to see you this Summer.

ArtSci on the Go

Looking for more ways to get more out of Arts & Sciences? Check out these resources to take ArtSci wherever you go!

Zev J. Handel, “Chinese Characters Across Asia: How the Chinese Script Came to Write Japanese, Korean, and Vietnamese”听()

Black Composers Project engages the School of Music faculty and students ()

Ladino Day Interview with Leigh Bardugo & MELC Professor Canan Bolel ()

Back to School Podcast 听with Liz Copland ()

Featured Podcast: “Ways of Knowing” (College of Arts & Sciences)

This podcast highlights how studies of the humanities can reflect everyday life. Through a partnership between and the 91探花, each episode features a faculty member from the 91探花College of Arts & Sciences, who discusses the work that inspires them and suggests resources to learn more about the topic.

Episode 1: Digital Humanities with Assistant Professor of English and Data Science, Anna Preus.

Episode 2: Paratext with Associate Professor of French, Richard Watts.

Episode 3: Ge’ez with Associate Professor of Middle Eastern Languages and Cultures, Hamza Zafer.

with Associate Professor听of Law, Societies and Justice, and of International Studies, Stephen Meyers.

with Professor of Mathematics and of the Comparative History of Ideas, Jayadev Athreya.

with Assistant Professor of Cinema and Media Studies, Golden Marie Owens.

From the School of Music

External Event:

The student-run Improvised Music Project presents performances by a rotating cast of 91探花jazz studies students, faculty, and special guests every first and third Wednesday, 6 to 10 pm, at (1508 11th Ave, Seattle, WA).

Event Dates:

June 18
July 2
July 16
July 30
August 6
August 20

From the Burke Museum

| 10:00 am – 8:00 pm

Admission to the Burke Museum is FREE, and the museum is open until 8 p.m. on the first Thursday of every month. Large crowds are expected, 听in advance.

CLOSING EXHIBIT | – Final day Sunday, June 22

Learn about the diversity and significance of trees with our hands-on activities. Play the tree-themed Hidden Husky gallery hunt 鈥� spot the five hidden huskies in the galleries to earn a special sticker prize!

OPENING EXHIBIT | – Saturday, September 13, 2025 to Sunday, August 30, 2026

Woven听in听Wool: Resilience听in听Coast Salish Weaving听showcases both historical and contemporary woven items 鈥� from blankets and tunics to hoods and skirts. Journey through the seasonal cycle of weaving, from gathering materials and spinning wool to dyeing with natural ingredients and weaving intricate designs. Along the way, learn听firsthand from weavers and gain听insight听into the deep cultural and scientific knowledge embedded听in听every strand.

From the Henry Art Gallery

OPENING EXHIBIT | – Saturday, July 26, 2025 to Sunday, January 11, 2026

Through the work in the exhibition, contemporary artists connect fragmented family narratives shaped by war, migration, and generational trauma to broader global contexts, creating new narratives that transform their difficult origins. With these artists as guides,听Spirit House听invites you to commune with your ancestors, reflect on significant memories, and journey through time and space.

CLOSING EXHIBIT | – Final day Sunday, July 27

This exhibition highlights听Sanctuary听(2017), a monumental tapestry commissioned by Western Bridge for Seattle鈥檚 Saint Mark鈥檚 Cathedral and now part of the Henry鈥檚 collection.

CLOSING EXHIBIT | – Final days, August 2025

For Bass鈥檚 project, commissioned and organized by the Henry, a series of fourteen stone benches is placed throughout Seattle鈥檚 , with two additional sculptures residing outside the Henry itself. Each bench is engraved with its own inscription and a silhouetted image applied in light-responsive pigment. The project examines themes of cultivation and wildness, the laws we impose to control human bodies, hierarchy and proximity, and stones as memorials, boundaries, and legislative markers.

CLOSING EXHIBIT | – Final day Sunday, August 25

Be flat听is听Tala Madani’s debut solo exhibition in Washington State, featuring recent and newly commissioned works that explore the influence of symbols, language, and mark-making on power dynamics and individual agency.

CLOSING EXHIBIT | – Final day Thursday, September 25

This focused exhibition features works from听Passing On听(2022), a series of collaged newspaper obituaries of influential feminist activists and organizers. The clippings, presented with Winant鈥檚 handwritten annotations, reflect on a lineage of non-biological inheritance and how language shapes memory and history.

June 2025

Wednesday, June 18, 2:00 – 5:00 pm | 听(Burke Museum)

Ravenstail weaving skills have returned to the hands of Northwest Coastal People, but their historical robes are still in museum collections. Mentor weaver Ksm Lx’sg瘫a瘫n, Ruth Hallows, and apprentice weaver Jay Hallows work in tandem with more than twenty weavers to symbolically restore historical Ravenstail robes by reweaving them and bringing them home to dance in ceremony.

Thursday, June 19, 10:00 am – 5:00 pm | (Burke Museum)

BLUEs.Weave will present two interrelated demonstrations of explorative Black American music in honor of the holiday of Juneteenth.

The first demonstration will feature original music works, lyrics, and improvisations meditating on the various forms and aesthetics of celebration as they appear throughout the sonic lineage of Black American music.听The second demonstration will be a live, collaborative composition session where BLUEs.Weave, culminating in a piece and performance reflecting on the importance of Juneteenth and Black freedom.

Thursday, June 19, 7:00 – 8:00 pm | ONLINE ONLY: (Center for Child & Family Well-Being)

Join the Center for Child & Family Well-Being for their monthly Community Drop-In with Shayla Collins. A time of mindfulness, self-compassion, and common humanity. You spend so much of your time caring for others, join for a very informal hour (or whatever you can commit to) of practice for yourself.

Thursday, June 19, 10:30 am – 2:00 pm | (Center for Labor Studies)

Join ILWU Local 19 and APRI Seattle for their 6th Annual Juneteenth Waterfront Freedom Celebration. There will be live entertainment, food, drinks, and guest speakers.

ILWU Local 19
3440 East Marginal Way S.
Seattle, WA

Wednesday, June 25, 11:00 am – 12:30 pm | (Chemistry)

Join the Department of Chemistry for a lunch-and-learn workshop with an Introduction to Optical Photothermal Infrared (O-PTIR), which provides submicron IR, simultaneous Raman, and co-located fluorescence. It has been used for a wide range of application areas.

Thursday, June 26, 7:00 – 8:30 pm | (Astrobiology)

Join the Institute for Data Intensive Research in Astrophysics & Cosmology (DiRAC) for a special celebration marking a new chapter in astronomy. This milestone represents over two decades of dedication and collaboration from the global Rubin community. DiRAC is especially proud to honor the UW’s Rubin Team, whose leadership and involvement have been instrumental.

This is more than an astronomy event 鈥� it鈥檚 a celebration of human curiosity, collaboration, and imagination. Whether you鈥檙e a student, researcher, space enthusiast, or simply someone who looks up at the night sky in wonder, you鈥檙e invited to be a part of this historic moment.

Thursday, June 26, 3:30 – 6:30 pm | Summer Celebration | Live Jazz @ the 91探花Club ( 91探花Alumni Association)

Join 91探花faculty, staff, and guests for an end-of-year afternoon of community and connection at the storied, scenic 91探花 Club. Enjoy live music performed by the Alliance of Improvisers, an ensemble composed of 91探花Jazz faculty, students, alumni musicians, and special guests.

This event is part of a series of community-building opportunities planned for the year ahead. As the University continues to assess and review future permanent directions for the building, the facility will remain closed for general use.

Wednesday, June 4 to Friday, July 4 | (Taiwan Studies)

This exhibition seeks to honor the memories of those who suffered and reflect on the lasting impact of the 228 Incident. Through archival photographs, personal testimonies, historical documents, and artistic interpretations, view a narrative of loss, resilience, and the ongoing pursuit of justice.

Information Sessions

June 24 |

June 25 |

June 26 |

June 27 |

June 30 |

July 2025

Wednesday, July 2, 12:30 pm | (School of Music)

Students of the 91探花School of Music perform in this听lunchtime concert series co-hosted听by 91探花Music and 91探花Libraries.

Small combos perform original music and arrangements of jazz standards, modern classics, and deep cuts from the popular music repertoire over two consecutive nights of performance.

May 30, 5:00 pm | Brechemin Auditorium

May 30, 7:00 – 9:00 pm | RailSpur

The School of Art + Art History + Design presents Another Day at The Orifice: 2024 MFA Thesis Exhibition running from May 28 through June 9 at RailSpur (Top Floor). Another Day at The Orifice features the cumulative thesis work of eight graduates receiving a Master of Fine Arts degree in Photo/Media, Painting + Drawing, and 3D4M: ceramics + glass + sculpture.

Free |

May 31, 2:30 pm | Communications Building

Join the Department of Classics’ undergraduate senior essay symposium. The symposium will be joined by senior essays and senior thesis writers for an informal discussion of their research in a round table format.

Free |

May 31, 7:30 pm | Meany Hall

Geoffrey Boers leads this year-end program by the 91探花 Symphony, led by David Alexander Rahbee, and combined 91探花Choirs.听听 听

Tickets |

June 1, 7:30 pm | Brechemin Auditorium

The 91探花Composition program presents a year-end concert听of works by undergraduate composers.

Free |

June 2, 10:00 am – 5:00 pm | Burke Museum

Hear about groundbreaking research from Burke and 91探花scientists, enjoy hundreds of specimens from the Burke鈥檚 collection, and celebrate all things fossilized with fossil digs, ancient animal identification, microfossil sorting, crafts, and more.

Tickets |

June 2, 3:00 pm | Brechemin Auditorium

Cello students of Sarah Rommel perform听a year-end studio recital.

Free |

In September, a team led by astronomers in the United Kingdom that they had detected the chemical phosphine in the thick clouds of Venus. The team鈥檚 reported detection, based on observations by two Earth-based radio telescopes, surprised many Venus experts. Earth鈥檚 atmosphere contains small amounts of phosphine, which may be produced by life. Phosphine on Venus generated buzz that the planet, often succinctly touted as a 鈥�,鈥� could somehow harbor life within its acidic clouds.

Since that initial claim, other science teams have on the reliability of the phosphine detection. Now, a team led by researchers at the 91探花 has used a robust model of the conditions within the atmosphere of Venus to revisit and comprehensively reinterpret the radio telescope observations underlying the initial phosphine claim. As they report in a accepted to the Astrophysical Journal and posted Jan. 25 to the preprint site arXiv, the U.K.-led group likely wasn鈥檛 detecting phosphine at all.

鈥淚nstead of phosphine in the clouds of Venus, the data are consistent with an alternative hypothesis: They were detecting sulfur dioxide,鈥� said co-author , a 91探花professor of astronomy. 鈥淪ulfur dioxide is the third-most-common chemical compound in Venus鈥� atmosphere, and it is not considered a sign of life.鈥�

The team behind the new study also includes scientists at NASA鈥檚 Caltech-based Jet Propulsion Laboratory, the NASA Goddard Space Flight Center, the Georgia Institute of Technology, the NASA Ames Research Center and the University of California, Riverside.

The UW-led team shows that sulfur dioxide, at levels plausible for Venus, can not only explain the observations but is also more consistent with what astronomers know of the planet鈥檚 atmosphere and its punishing chemical environment, which includes clouds of sulfuric acid. In addition, the researchers show that the initial signal originated not in the planet鈥檚 cloud layer, but far above it, in an upper layer of Venus鈥� atmosphere where phosphine molecules would be destroyed within seconds. This lends more support to the hypothesis that sulfur dioxide produced the signal.

Both the purported phosphine signal and this new interpretation of the data center on radio astronomy. Every chemical compound absorbs unique wavelengths of the , which includes radio waves, X-rays and visible light. Astronomers use radio waves, light and other emissions from planets to learn about their chemical composition, among other properties.

In 2017 using the , or JCMT, the U.K.-led team discovered a feature in the radio emissions from Venus at 266.94 gigahertz. Both phosphine and sulfur dioxide absorb radio waves near that frequency. To differentiate between the two, in 2019 the same team obtained follow-up observations of Venus using the , or ALMA. Their analysis of ALMA observations at frequencies where only sulfur dioxide absorbs led the team to conclude that sulfur dioxide levels in Venus were too low to account for the signal at 266.94 gigahertz, and that it must instead be coming from phosphine.

In this new study by the UW-led group, the researchers started by modeling conditions within Venus鈥� atmosphere, and using that as a basis to comprehensively interpret the features that were seen 鈥� and not seen 鈥� in the JCMT and ALMA datasets.

鈥淭his is what鈥檚 known as a radiative transfer model, and it incorporates data from several decades鈥� worth of observations of Venus from multiple sources, including observatories here on Earth and spacecraft missions like ,鈥� said lead author Andrew Lincowski, a researcher with the 91探花Department of Astronomy.

The team used that model to simulate signals from phosphine and sulfur dioxide for different levels of Venus鈥� atmosphere, and how those signals would be picked up by the JCMT and ALMA in their 2017 and 2019 configurations. Based on the shape of the 266.94-gigahertz signal picked up by the JCMT, the absorption was not coming from Venus鈥� cloud layer, the team reports. Instead, most of the observed signal originated some 50 or more miles above the surface, in Venus鈥� mesosphere. At that altitude, harsh chemicals and ultraviolet radiation would shred phosphine molecules within seconds.

鈥淧hosphine in the mesosphere is even more fragile than phosphine in Venus鈥� clouds,鈥� said Meadows. 鈥淚f the JCMT signal were from phosphine in the mesosphere, then to account for the strength of the signal and the compound鈥檚 sub-second lifetime at that altitude, phosphine would have to be delivered to the mesosphere at about 100 times the rate that oxygen is pumped into Earth鈥檚 atmosphere by photosynthesis.鈥�

The researchers also discovered that the ALMA data likely significantly underestimated the amount of sulfur dioxide in Venus鈥� atmosphere, an observation that the U.K.-led team had used to assert that the bulk of the 266.94-gigahertz signal was from phosphine.

鈥淭he antenna configuration of ALMA at the time of the 2019 observations has an undesirable side effect: The signals from gases that can be found nearly everywhere in Venus鈥� atmosphere 鈥� like sulfur dioxide 鈥� give off weaker signals than gases distributed over a smaller scale,鈥� said co-author Alex Akins, a researcher at the Jet Propulsion Laboratory.

This phenomenon, known as spectral line dilution, would not have affected the JCMT observations, leading to an underestimate of how much sulfur dioxide was being seen by JCMT.

鈥淭hey inferred a low detection of sulfur dioxide because of that artificially weak signal from ALMA,鈥� said Lincowski. 鈥淏ut our modeling suggests that the line-diluted ALMA data would have still been consistent with typical or even large amounts of Venus sulfur dioxide, which could fully explain the observed JCMT signal.鈥�

鈥淲hen this new discovery was announced, the reported low sulfur dioxide abundance was at odds with what we already know about Venus and its clouds,鈥� said Meadows. 鈥淥ur new work provides a complete framework that shows how typical amounts of sulfur dioxide in the Venus mesosphere can explain both the signal detections, and non-detections, in the JCMT and ALMA data, without the need for phosphine.鈥�

With science teams around the world following up with fresh observations of Earth鈥檚 cloud-shrouded neighbor, this new study provides an alternative explanation to the claim that something geologically, chemically or biologically must be generating phosphine in the clouds. But though this signal appears to have a more straightforward explanation 鈥� with a toxic atmosphere, bone-crushing pressure and some of our solar system鈥檚 hottest temperatures outside of the sun 鈥� Venus remains a world of mysteries, with much left for us to explore.

Additional co-authors are at the JPL, at UC Riverside, and at the Goddard Space Flight Center, 91探花researcher , at Georgia Tech and at NASA Ames. The research was funded by the NASA Astrobiology Program and performed at the NExSS Virtual Planetary Laboratory.

For more information, contact Meadows at meadows@uw.edu, Akins at alexander.akins@jpl.nasa.gov and Lincowski at alinc@uw.edu.

The TRAPPIST-1 star system is home to the largest batch of roughly Earth-size planets ever found outside our solar system. some 40 light-years away, these seven rocky siblings offer a glimpse at the tremendous variety of planetary systems that likely fill the universe.

A accepted by the Planetary Science Journal shows that the planets share similar densities. That could mean they all contain roughly the same ratio of materials thought to be common to rocky planets, such as iron, oxygen, magnesium and silicon. If so, then while the might be similar to each other, they appear to differ notably from Earth: They鈥檙e about 8% less dense than they would be if they had the same chemical composition as our planet.

These findings give astronomers new data that they鈥檙e using to try to pin down the precise composition of these planets, and compare them not just to Earth, but to all the rocky planets in our solar system, according to lead author , a 91探花 professor of astronomy.

鈥淭his is one of the most precise characterizations of a set of rocky exoplanets, which gave us high-confidence measurements of their diameters, densities and masses,鈥� said Agol. 鈥淭his is the information we needed to make hypotheses about their composition and understand how these planets differ from the rocky planets in our solar system.鈥�

Since the initial detection in 2016 of the TRAPPIST-1 worlds, scientists have studied this planetary family with multiple space- and ground-based telescopes, including NASA’s now-retired and . Spitzer alone provided over 1,000 hours of targeted observations of the system before . Since they鈥檙e too small and faint to view directly, all seven exoplanets were found via the so-called transit method: looking for dips in the star’s brightness created when the planets cross in front of it.

had shown that the planets are roughly the size and mass of Earth and thus must also be 鈥� as opposed to gas-dominated worlds like Jupiter and Saturn. This new study offers the most precise density measurements to date for any group of exoplanets.

“The night sky is full of planets, and it’s only been within the last 30 years that we’ve been able to start unraveling their mysteries,” said co-author of the University of Zurich. “The TRAPPIST-1 system is fascinating because around this one star we can learn about the diversity of rocky planets within a single system. And we can actually learn more about a planet by studying its neighbors as well, so this system is perfect for that.”

The team 鈥� which includes scientists based in the United States, Switzerland, France, the United Kingdom and Morocco 鈥� used observations of the starlight dips and precise measurements of the timing of the planets’ orbits to make detailed measurements of each planet鈥檚 mass and diameter, and from there to determine its density. Agol and 91探花co-authors Zachary Langford and , a professor of astronomy, analyzed data and performed computer simulations that constrained the orbits of the TRAPPIST-1 planets and calculated their densities.

With more precise measurements of an object鈥檚 density, we can know more about its composition. A baseball and a paperweight may be the same size, but the baseball is much lighter. Width and weight together reveal each object’s density, and from there it is possible to infer that the baseball is made of lighter materials, like string and leather, while the paperweight has a heavier composition, like glass or metal.

In our own solar system, the densities of the eight planets vary widely. The gas giants 鈥� Jupiter, Saturn, Uranus and Neptune 鈥� are larger, but much less dense than the four rocky planets. Earth, Venus and Mars have similar densities, but Mercury contains a much higher percentage of iron, so although it is the solar system’s smallest planet in diameter, Mercury has the second highest density of all eight planets.

The seven TRAPPIST-1 planets, on the other hand, all share a similar density, which makes the system quite different from our own. The difference in density between the TRAPPIST-1 planets and Earth, Venus and Mars, may seem small 鈥� about 8% 鈥� but it is significant on a planetary scale. For example, one way to explain the lower density is that the TRAPPIST-1 planets have a similar composition to Earth, but with a lower percentage of iron 鈥� about 21% compared to Earth’s 32%, according to the study.

Alternatively, the iron in the TRAPPIST-1 planets might be infused with high levels of oxygen, forming iron oxide, or rust. The additional oxygen would decrease the planets’ densities. The surface of Mars gets its red tint from iron oxide, but like its three terrestrial siblings, it has a core composed of non-oxidized iron. By contrast, if the lower density of the TRAPPIST-1 planets were caused entirely by oxidized iron, then the planets would have to be rusty throughout and could not have iron cores.

Agol said the answer might be a combination of the two scenarios 鈥� less iron overall and some oxidized iron.

The team also looked into whether the surface of each planet could be covered with water, which is even lighter than rust and which would change the planet’s overall density. If that were the case, water would have to account for about 5% of the total mass of the outer four planets. By comparison, water makes up less than 0.1% of Earth’s total mass. The three inner TRAPPIST-1 planets, positioned too close to their star for water to remain a liquid under most circumstances, would require hot, dense atmospheres like on Venus, where water could remain bound to the planet as steam. But this explanation seems less likely because it would be a coincidence for all seven planets to have just enough water present to have such similar densities, according to Agol.

When it launches, NASA鈥檚 James Webb Space Telescope should have the capabilities to probe this system further, including gathering more detailed information about the atmospheres of the seven TRAPPIST-1 worlds.

鈥淭here are many more questions to answer about TRAPPIST-1 and its worlds,鈥� said Agol. 鈥淎nd in a way, answering them helps us understand our own solar system, too.鈥�

Agol and Meadows are members of the NASA NExSS Virtual Planetary Laboratory team and the 91探花Astrobiology Program. Agol鈥檚 involvement in the study was funded by the National Science Foundation, NASA, the Guggenheim Foundation and the Virtual Planetary Laboratory.

For more information, contact Agol at agol@uw.edu.

Adapted from a by NASA鈥檚 Jet Propulsion Laboratory.

Many of these online opportunities are streamed through Zoom. All 91探花faculty, staff, and students have access to听.听

Velvet Sweatshops and Algorithmic Cruelty: Labor in the Global Tech Economy

One Nation, Many Stories–30 years of German Unity

October 10, 11:00 AM – 12:30 PM |

October 3, 2020 marks the 30th anniversary of German unification. While formal unification took barely a year, it turns out that unity takes generations. Continuing differences in living standards, pensions, political orientations, or democratic values indicate that the process of unifying former East and West Germany is a multi-generational project. Have Germans dealt adequately with their separate pasts in order to craft a joint 21st-century political identity? Three distinguished experts on German politics, society, and culture, Marianne Birthler,听Michael Z眉rn, and Joyce听Mushaben,听will discuss this and other questions.

Free |

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Check out UWAA’s Stronger Together web page for听more digital engagement opportunities.

Scientists have discovered thousands of , including dozens of terrestrial 鈥� or rocky 鈥� worlds in the around their parent stars. A promising approach to search for signs of life on these worlds is to probe exoplanet atmospheres for 鈥渂iosignatures鈥� 鈥� quirks in chemical composition that are telltale signs of life. For example, thanks to photosynthesis, our atmosphere is nearly 21% oxygen, a much higher level than expected given Earth鈥檚 composition, orbit and parent star.

Finding biosignatures is no straightforward task. Scientists use data about how exoplanet atmospheres interact with light from their parent star to learn about their atmospheres. But the information, or spectra, that they can gather using today鈥檚 ground- and space-based telescopes is too limited to measure atmospheres directly or detect biosignatures.

Exoplanet researchers such as , a professor of astronomy at the 91探花, are focused on what forthcoming observatories, like the , or JWST, could measure in exoplanet atmospheres. On Feb. 15 at the in Seattle, Meadows, a principal investigator of the UW鈥檚 , will deliver a talk to summarize what kind of data these new observatories can collect and what they can reveal about the atmospheres of terrestrial, Earth-like exoplanets. Meadows sat down with 91探花News to discuss the promise of these new missions to help us view exoplanets in a new light.

What changes are coming to the field of exoplanet research?

In the next five to 10 years, we鈥檒l potentially get our first chance to observe the atmospheres of terrestrial exoplanets. This is because new observatories are set to come online, including the James Webb Space Telescope and ground-based observatories like the . A lot of our recent work at the Virtual Planetary Laboratory, as well as by colleagues at other institutions, has focused on simulating what Earth-like exoplanets will 鈥渓ook鈥� like to the JWST and ground-based telescopes. That allows us to understand the spectra that these telescopes will pick up, and what those data will and won鈥檛 tell us about those exoplanet atmospheres.

What types of exoplanet atmospheres will the JWST and other missions be able to characterize?

Our targets are actually a select group of exoplanets that are nearby 鈥� within 40 light years 鈥� and orbit very small, cool stars. For reference, the Kepler mission identified exoplanets around stars that are more than 1,000 light years away. The smaller host stars also help us get better signals on what the planetary atmospheres are made of because the thin layer of planetary atmosphere can block more of a smaller star鈥檚 light.

So there are a handful of exoplanets we鈥檙e focusing on to look for signs of habitability and life. All were identified by ground-based surveys like and its successor, 鈥� both run by the University of Li猫ge 鈥� as well as the run by Harvard. The most well-known exoplanets in this group are probably the seven terrestrial planets orbiting . TRAPPIST-1 is an M-dwarf star 鈥� one of the smallest you can have and still be a star 鈥� and its seven exoplanets span interior to and beyond the habitable zone, with three in the habitable zone.

We鈥檝e identified TRAPPIST-1 as the best system to study because this star is so small that we can get fairly large and informative signals off of the atmospheres of these worlds. These are all cousins to Earth, but with a very different parent star, so it will be very interesting to see what their atmospheres are like.

What have you learned so far about the atmospheres of the TRAPPIST-1 exoplanets?

The astronomy community has taken observations of the TRAPPIST-1 system, but we haven鈥檛 seen anything but 鈥渘on-detections.鈥� That can still tell us a lot. For example, observations and models suggest that these exoplanet atmospheres are less likely to be dominated by hydrogen, the lightest element. That means they either don鈥檛 have atmospheres at all, or they have relatively high-density atmospheres like Earth.

No atmospheres at all? What would cause that?

M-dwarf stars have a very different history than our own sun. After their infancy, sun-like stars brighten over time as they undergo fusion.

M-dwarfs start out big and bright, as they gravitationally collapse to the size they will then have for most of their lifetimes. So, M-dwarf planets could be subjected to long periods of time 鈥� perhaps as along as a billion years 鈥� of high-intensity luminosity. That could strip a planet of its atmosphere, but volcanic activity can also replenish atmospheres. Based on their densities, we know that many of the TRAPPIST-1 worlds are likely to have reservoirs of compounds 鈥� at much higher levels than Earth, actually 鈥� that could replenish the atmosphere. The first significant JWST results for TRAPPIST-1 will be: Which worlds retained atmospheres? And what types of atmospheres are they?

I鈥檓 quietly optimistic that they do have atmospheres because of those reservoirs, which we鈥檙e still detecting. But I鈥檓 willing to be surprised by the data.

What types of signals will the JWST and other observatories look for in the atmospheres of TRAPPIST-1 exoplanets?

Probably the easiest signal to look for will be the presence of carbon dioxide.

Is CO2 a biosignature?

Not on its own, and not just from a single signal. I always tell my students 鈥� look right, look left. Both Venus and Mars have atmospheres with high levels of CO2, but no life.

In Earth鈥檚 atmosphere, CO2 levels adjust with our seasons. In spring, levels draw down as plants grow and take CO2 out of the atmosphere. In autumn, plants break down and CO2 rises. So if you see seasonal cycling, that might be a biosignature. But seasonal observations are very unlikely with JWST.

Instead, JWST can look for another potential biosignature, methane gas in the presence of CO2. Methane should normally have a short lifetime with CO2. So if we detect both together, something is probably actively producing methane. On Earth, most of the methane in our atmosphere is produced by life.

What about detecting oxygen?

Oxygen alone is not a biosignature. It depends on its levels and what else is in the atmosphere. You could have an oxygen-rich atmosphere from the loss of an ocean, for example: Light splits water molecules into hydrogen and oxygen. Hydrogen escapes into space, and oxygen builds up into the atmosphere.

The JWST likely won鈥檛 directly pick up oxygen from 鈥� the biosphere we鈥檙e used to now. The Extremely Large Telescope and related observatories might be able to, because they鈥檒l be looking at a different wavelength than the JWST, where they will have a better chance of seeing oxygen. The JWST will be better for detecting biospheres similar to what we had on Earth billions of years ago, and for differentiating between different types of atmospheres.

What are some of the different types of atmospheres that TRAPPIST-1 exoplanets might possess?

The M-dwarf鈥檚 high-luminosity phase might drive a planet toward an atmosphere with a runaway greenhouse effect, like Venus. As I said earlier, you could lose an ocean and have an oxygen-rich atmosphere. A third possibility is to have something more Earth-like.

Let鈥檚 talk about that second possibility. How could JWST reveal an oxygen-rich atmosphere if it can鈥檛 detect oxygen directly?

The beauty of the JWST is that it can pick up processes happening in an exoplanet鈥檚 atmosphere. It will pick up the signatures of collisions between oxygen molecules, which will happen more often in an oxygen-rich atmosphere. So we likely can鈥檛 see oxygen amounts associated with a photosynthetic biosphere. But if a much larger amount of oxygen was left behind from ocean loss, we can probably see the collisions of oxygen in the spectrum, and that鈥檚 probably a sign that the exoplanet has lost an ocean.

So, JWST is unlikely to give us conclusive proof of biosignatures but may provide some tantalizing hints, which require further follow-up and 鈥� moving forward 鈥� thinking about new missions beyond the JWST. NASA is already considering new missions. What would we like their capabilities to be?

That also brings me to a very important point: Exoplanet science is massively interdisciplinary. Understanding the environment of these worlds requires considering orbit, composition, history and host star 鈥� and requires the input of astronomers, geologists, atmospheric scientists, stellar scientists. It really takes a village to understand a planet.

For more information, contact Meadows at meadows@uw.edu.

Very occasionally, Earth gets bombarded by a large meteorite. But every day, our planet gets pelted by space dust, micrometeorites that collect on Earth’s surface.

A 91探花 team looked at very old samples of these small meteorites to show that the grains could have reacted with carbon dioxide on their journey to Earth. Previous work suggested the meteorites ran into oxygen, contradicting theories and evidence that the Earth’s early atmosphere was virtually devoid of oxygen. The new was published this week in the open-access journal Science Advances.

“Our finding that the atmosphere these micrometeorites encountered was high in carbon dioxide is consistent with what the atmosphere was thought to look like on the early Earth,” said first author , a 91探花doctoral student in Earth and space sciences.

At 2.7 billion years old, these are the oldest known micrometeorites. They were collected in limestone in the Pilbara region of Western Australia and fell during the Archean eon, when the sun was weaker than today. A 2016 paper by the team that discovered the samples suggested they at the time they fell to Earth.

That interpretation would contradict current understandings of our planet’s early days, which is that oxygen rose during the “,” almost half a billion years later.

Knowing the conditions on the early Earth is important not just for understanding the history of our planet and the conditions when life emerged. It can also help inform the search for life on other planets.

“Life formed more than 3.8 billion years ago, and how life formed is a big, open question. One of the most important aspects is what the atmosphere was made up of 鈥� what was available and what the climate was like,” Lehmer said.

The new study takes a fresh look at interpreting how these micrometeorites interacted with the atmosphere, 2.7 billion years ago. The sand-sized grains hurtled toward Earth at up to 20 kilometers per second. For an atmosphere of similar thickness to today, the metal beads would melt at about 80 kilometers elevation, and the molten outer layer of iron would then oxidize when exposed to the atmosphere. A few seconds later the micrometeorites would harden again for the rest of their fall. The samples would then remain intact, especially when protected under layers of sedimentary limestone rock.

The previous paper interpreted the oxidization on the surface as a sign that the molten iron had encountered molecular oxygen. The new study uses modeling to ask whether carbon dioxide could have provided the oxygen to produce the same result. A computer simulation finds that an atmosphere made up of from 6% to more than 70% carbon dioxide could have produced the effect seen in the samples.

“The amount of oxidation in the ancient micrometeorites suggests that the early atmosphere was very rich in carbon dioxide,” said co-author , a 91探花professor of Earth and space sciences.

For comparison, carbon dioxide concentrations today are rising and are currently at about 415 parts per million, or 0.0415% of the atmosphere’s composition.

High levels of carbon dioxide, a heat-trapping greenhouse gas, would counteract the sun’s weaker output during the Archean era. Knowing the exact concentration of carbon dioxide in the atmosphere could help pinpoint air temperature and and acidity of the oceans during that time.

More of the ancient micrometeorite samples could help narrow the range of possible carbon dioxide concentrations, the authors wrote. Grains that fell at other times could also help trace the history of Earth’s atmosphere through time.

“Because these iron-rich micrometeorites can oxidize when they are exposed to carbon dioxide or oxygen, and given that these tiny grains presumably are preserved throughout Earth’s history, they could provide a very interesting proxy for the history of atmospheric composition,” Lehmer said.

Other co-authors are , a 91探花professor emeritus of astronomy; , a 91探花professor of Earth and space sciences; and , a former 91探花undergraduate who is now at Rutgers University. The research was funded by NASA, the 91探花Astrobiology Program, the 91探花Virtual Planetary Laboratory and the Simons Foundation’s Collaboration on the Origins of Life.

For more information, contact Lehmer at olehmer@uw.edu or Catling at 206-543-8653 or dcatling@uw.edu.

91探花 astrobiologist has created software that simulates multiple aspects of planetary evolution across billions of years, with an eye toward finding and studying potentially habitable worlds.

Barnes, a 91探花assistant professor of astrobiology, astronomy and data science, released the first version of VPLanet, his virtual planet simulator, in August. He and his co-authors described it in a accepted for publication in the Publications of the Astronomical Society of the Pacific.

鈥淚t links different physical processes together in a coherent manner,” he said, “so that effects or phenomena that occur in some part of a planetary system are tracked throughout the entire system. And ultimately the hope is, of course, to determine if a planet is able to support life or not.鈥�

VPLanet’s mission is three-fold, Barnes and co-authors write. The software can:

• simulate newly discovered exoplanets to assess their potential to possess surface liquid water, which is a key to life on Earth and indicates the world is a viable target in the search for life beyond Earth
• model diverse planetary and star systems regardless of potential habitability, to learn about their properties and history, and
• enable transparent and open science that contributes to the search for life in the universe

The first version includes modules for the internal and magnetic evolution of terrestrial planets, climate, atmospheric escape, tidal forces, orbital evolution, rotational effects, stellar evolution, planets orbiting binary stars and the gravitational perturbations from passing stars.

It鈥檚 designed for easy growth. Fellow researchers can write new physical modules 鈥渁nd almost plug and play them right in,” Barnes said. VPLanet can also be used to complement more sophisticated tools such as machine learning algorithms.

An important part of the process, he said, is validation, or checking physics models against actual previous observations or past results, to confirm that they are working properly as the system expands.

鈥淭hen we basically connect the modules in a central area in the code that can model all members of a planetary system for its entire history,” Barnes said.

And though the search for potentially habitable planets is of central importance, VPLanet can be used for more general inquiries about planetary systems.

鈥淲e observe planets today, but they are billions of years old,鈥� he said. This is a tool that allows us to ask: ‘How do various properties of a planetary system evolve over time?’鈥�

The project’s history dates back almost a decade to a Seattle meeting of astronomers called “Revisiting the Habitable Zone” convened by , principal investigator of the UW-based , with Barnes. The habitable zone is the swath of space around a star that allows for orbiting rocky planets to be temperate enough to have liquid water at their surface, giving life a chance.

They recognized at the time, Barnes said, that knowing if a planet is within its star’s habitable zone simply isn’t enough information: “So from this meeting we identified a whole host of physical processes that can impact a planet’s ability to support and retain water.”

Barnes discussed VPLanet and presented a tutorial on its use at the recent AbSciCon19 worldwide astrobiology conference, held in Seattle.

The research was done through the Virtual Planetary Laboratory and the source code is available .

Barnes鈥檚 other faculty co-authors are astronomy professor ; , professor of atmospheric sciences; and research scientist . Other 91探花co-authors are doctoral students , , and ; and undergraduate researchers Caitlyn Wilhelm, Benjamin Guyer and Diego McDonald.

Other co-authors are of the Carnegie Institution for Science; of the Flatiron Institute, of the Max Planck Institute for Astronomy in Heidelberg, Germany, of the University of Bern, of the NASA Goddard Space Flight Center and of Weber State University.

The research was funded by a grant from the NASA Astrobiology Program鈥檚 Virtual Planetary Laboratory team, as part of the research coordination network, or NExSS.

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For more information, contact Barnes at 206-543-8979 or rkb9@uw.edu.

Grant numbers

VPL under cooperative agreement #NNA13AA93A

NASA grants #NNX15AN35G, #13-13-NA17 0024, and #80NSSC18K0829

NASA Earth and Space Science Fellowship Program grant #80NSSC17K0482

inflated a big black fabric tent in the lobby of the Hyatt Regency Hotel on Wednesday and stood outside it inviting passers-by: “Come on in and watch the show 鈥� we’re talking about astrobiology.”

Barnes, a 91探花 research assistant professor of astronomy, was showing off the department’s to colleagues at , the national conference on astrobiology, . The conference is happening all week at the Hyatt, and dozens of 91探花faculty and students are involved.

The tent is about 10 feet tall and 20 feet across and stays upright with the help of a high-powered fan. Its graphics come via Microsoft’s World Wide Telescope. 91探花astronomy faculty and students to conduct outreach about astronomy to area schools, and have been educating (and entertaining) thousands of students about the cosmos since.

But recently, Barnes and graduate students have been using the Mobile Planetarium to tell K-12 students about astrobiology. It’s a hit with middle school students especially, he said.

“They get excited about it. It鈥檚 a very visceral experience, very immersive, and there’s often a lot of screaming as they move through the universe,” Barnes said, smiling. “You can see they’re engaged.”

Astrobiology graduate students were conducting the shows inside the tent on Wednesday, starting a new presentation every so often as people filed by and stepped 鈥� climbed, really 鈥� through a fabric doorway into the dark interior.

There mid-Wednesday, astronomy doctoral students David Graham, then , gave engaging, illustrated lectures to visitors huddled in the darkness inside. Aided by graphics displayed in color against the rounded tent ceiling, they in turn took their audience from scenes of “extremophile” creatures living on Earth out through the solar system and into deep space 鈥� so far out, whole galaxies appear as mere dots.

Garcia talked of the “big questions” astrobiologists want to answer, leading with the most basic: “Are we alone in the universe?”

He added: “Personally I think this also tells me that life is precious. Even if planets are common we haven’t seen life on them yet, so the life on our own planet is really precious as well.

“So, it’s not just a scientific pursuit 鈥� astrobiology 鈥� but it’s also, how do we relate to our environment? And I think it’s really beautiful in that way.”

Barnes does assessments before and after his school visits and said they show the students enjoy the presentation, even if a little part of that might be just being away from class.

“But it’s all just about getting them to remember this experience. They remember they had a good experience 鈥� that’s still a win.”

He said one thing he definitely sees is that “people from all over, whatever their background, they do ‘get’ this 鈥� they go, ‘Whoa, there’s no life out there that we know, but that’s interesting and maybe I can think about this.’

“And the best, of course, is every time you go you get two or three kids who say, ‘This is really cool 鈥� maybe I want to study planets.'”

Barnes also reported on the 91探花Mobile Planetarium to the conference in a separate session Thursday. He hopes to keep it going and is looking for further funding for the project.

Soon he was back out front, looking for the next audience.

“We’re talking astrobiology. Want to come in and see the show?”

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For more information, contact Barnes at rkb9@uw.edu.