Editor’s Note: This week we’re at the 53rd meeting of the AAS Division for Planetary Sciences. Along with a team of authors from Astrobites, we will be writing updates on selected events at the meeting. You can read the second and final recap here or at astrobites.com after the conclusion of the meeting. The usual posting schedule for AAS Nova will resume next week.
Monday Press Conference (by Macy Huston)
Recurrent Activity from a Main Belt Comet: Colin Chandler (Northern Arizona University)
The first speaker of the DPS 2021 press conference series was PhD candidate Colin Chandler, who described the recurrent activity of asteroid (248370) 2005 QN173 (QN from here on). “Active” asteroids are those that have comet-like features such as tails. They are valuable for studying where water in the solar system is now and where Earth’s water came from. The new active asteroid QN was discovered in the main asteroid belt in July 2021. Archival data from the Blanco 4-meter telescope in Chile revealed that the asteroid had been active in the past in July 2016, roughly one orbital period ago. This is only the 8th known recurrently active asteroid, and the cause of the activity is thought to be ice sublimation. It’s considered a probable “main belt comet.” Press release
The Nucleus and Dust Tail of an Active Asteroid: Henry Hsieh (Planetary Science Institute)
The next speaker, Dr. Henry Hsieh, presented more information on the same QN object. Asteroids and comets are classically considered to be distinct objects. Asteroids are typically rocky, inert, and on relatively close-in circular orbits, whereas comets are typically icy, active, and on elongated orbits, spending most of their time far from the Sun. Hsieh reviewed the existence of active asteroids, which have only been recognized within the past 15 years and are not yet well understood. QN’s recent activity was discovered by the ATLAS survey telescope on Mauna Loa in Hawaii. Follow-up efforts were coordinated among 5 telescopes on 3 continents, aiming to learn as much as possible about the object. In addition to these planned observations, the comet was serendipitously picked up by 4 additional telescopes, which allowed for the determination of the nucleus’s size and composition. They found that QN has a 2-mile-wide nucleus with a 450,000-mile-long and 900-mile-wide tail. The narrow tail indicates slow dust and gas release. Further study of the nucleus’s rotation will help determine whether fast rotation contributes to the activity caused at least partially by sublimation. Press release
More Evidence that Pluto’s Atmosphere is Freezing Out: Eliot Young (Southwest Research Institute)
Next, Dr. Eliot Young presented a study of Pluto’s atmosphere. Pluto gets very little sunlight at its orbit beyond 30 AU. Its tenuous atmosphere is supported by the vapor pressure of N2 ice, which is a very steep function of temperature. Pluto’s atmosphere gradually increased in size from 1989–2015, but it is expected to eventually “freeze out” and disappear as the dwarf planet moves farther from the Sun. Pluto passed in front of (occulted) a V=13 magnitude star in 2018, allowing for detailed study of its atmosphere. The light curve of the dwarf planet’s occultation event is affected by its atmospheric surface pressure and haze opacity. The previous trend in Pluto’s surface pressure predicted the 2018 value to be 14.4 microbar, but the measurement was 11.4 microbar, which is roughly equivalent to the 2015 value measured by New Horizons. This indicates that Pluto’s warming trend has ended, and its atmosphere may be headed towards freeze out. Previously, the haze opacity had correlated with the solar cycle, but this was found to be coincidental, as the drop in solar activity between 2015–2018 occurred alongside an increase in haze opacity. Press release
Telescopic and Lab Investigations of The Surfaces of Active and Cometary Near-Earth Objects: Theodore Kareta (University of Arizona)
The final presentation of this session was given by Dr. Teddy Kareta about comets and meteor showers. (3200) Phaethon is the origin of the Geminid meteor shower, but it is atypical of active comets. It is blue, stays relatively close to the Sun, and is not very active. Phaethon is thought to be related to a smaller object called (155140) 2005 UD — they have similar colors, orbits, low activity, and are associated with meteor showers. Observed in the near-infrared, however, the objects’ spectra are quite different from one another. A possible explanation is that they are made of the same material but have been heated to different extents. In order to test these conditions, the group built a new laboratory device to measure how a meteorite’s reflectivity changes in a near-vacuum at different temperatures. When heated to a temperature similar to Phaethon’s peak temperature, the laboratory spectra looked similar to Phaethon’s observed spectra. This was not the case for material heated to the temperature of 2005 UD, though. This suggests that the objects’ similarity in appearance is coincidental rather than indicative of a common origin.
View of Olympus Mons from HOPE, Feb 26th 2021. [Emirates eXploration Imager (EXI), UAE Space Agency]
Mars Plenary (by Sasha Warren)
This year’s Mars Plenary journeyed all the way from the Martian core to its upper atmosphere, providing updates on five ongoing missions including new results, technical challenges, and goals for future investigations. Summary lightning talks were followed by a Q&A session, moderated by Jennifer Hanley and Brian Jackson, that covered every topic from Mars’s formation and early history to Mars spacecraft design, making the most of the wide array of expertise brought by the five presenters.
Deputy Project Manager for Science for the Emirates HOPE mission Hessa Almatroushi shared stunning new images from the probe’s orbit insertion in February and detailed the suite of instruments that has since been monitoring the Mars atmosphere in the visible, ultraviolet, and infrared. Over the coming years, the mission will provide a global picture of how different atmospheric species — like hydrogen and oxygen — respond to changes in the time of day, season, solar activity, and Martian weather (especially dust storms!).
Shannon Curry, the new PI of NASA’s MAVEN mission, spoke about how the results from MAVEN so far can be used to calculate how much of Mars’s atmosphere has been lost over the past 3 billion years, and how important the effects of changing solar activity and dust storms are, particularly for the escape of water. The upcoming solar maximum in 2024 will provide an opportunity to measure atmospheric escape rates under the most extreme conditions yet as it will coincide with Mars’s dust storm season — and the MAVEN team can’t wait. From the Q&A session, it seems that there will be a lot of potential for MAVEN and the HOPE probe to work together to create a full picture of the Mars atmosphere from the surface to deep into space when this exciting season comes around.
Reporting results from closer to the surface, Matt Golombek from NASA’s Jet Propulsion Laboratory detailed the unprecedented success of the Ingenuity helicopter that arrived on Mars with the Perseverance rover. In just a few months, it has already flown 13 times — smashing the intended five technology demonstration flights — and is now being used to help plan the rover’s path across the Séítah region in Jezero Crater. Matt also dropped hints about the potential for future helicopter missions that could hop for hundreds of kilometers across the Mars surface at a fraction of the cost of a rover mission, with the potential to revolutionize how we explore the Red Planet! Kenneth Farley, lead project scientist for NASA’s Mars 2020 Perseverance rover, provided an update on the Perseverance mission so far, announcing a new paper confirming the hypothesis that the fan in Jezero Crater formed in an ancient lake environment. Not everything has been quite so straightforward, however, as the rocks that the rover has been driving across for nearly 2 km have been almost impossible to characterize because of their thick surface coating likely caused by millions of years of sandblasting by Martian dust and wind. Luckily, Perseverance has been able to scratch away some of this coating to reveal what look to be volcanic rocks beneath, possibly from lava flows. In addition to answering the question of what Jezero’s crater floor is made of (something that couldn’t be answered from orbital data alone!), these rocks also appear to have interacted with water at some time in their history. The exact minerals present — which are important for determining the temperature and chemical conditions that the rocks experienced — aren’t fully known yet but the Perseverance team plans to continue exposing fresh surfaces and measuring them with all the different tools it has available. Perhaps the most exciting part, though, is that these volcanic rocks represent the first of 40 samples that Perseverance will cache on Mars in anticipation of a future Mars Sample Return mission.
Bruce Banerdt took the conversation beneath the Martian surface, sharing the successes (and struggles) of the InSight mission, which has now achieved its primary science goal of revealing the interior structure of Mars. The biggest surprise is that Mars’s metallic core has a diameter almost 50 km larger than predicted, making it less dense than previously thought. This has triggered many new experimental and theoretical studies of the core’s elemental composition to try to match the new data. In the Q&A, Bruce shared his excitement that the mission was able to “break” something about our understanding of Mars, reminding the audience that it’s always most interesting, and most scientifically useful, for new data to disprove well-established theories.
If you’re attending DPS and missed this session, check the DPS 53 Slack workspace for summary slides from each of the presenters, and any ongoing discussion throughout the meeting. The full presentations and the plenary session recording can be found on the Monday tab of the Scientific Oral Sessions within the virtual meeting space.
Women in Planetary Sciences Discussion (by Kerry Hensley)
The hosts, Northern Arizona University graduate student Audrey Martin and SOFIA Associate Project Scientist Maggie McAdam, began by acknowledging what an intense and challenging year this has been — in the United States alone, we’ve experienced the continuation of a pandemic that has claimed hundreds of thousands of lives, wildfires and other extreme weather events driven by climate change, a contentious national election, an increase in hate crimes against Asian Americans, and continued violence perpetrated against members of the Black community. While scientists may like to think that these events are entirely separate from our work, it’s impossible to separate who we are as scientists from who we are as people. For scientists belonging to one or more communities historically impacted by racism, sexism, and other forms of discrimination, the challenges of the past year have magnified the impacts of inequality, both within planetary science and beyond the field.
The hosts reminded the audience that progress toward equity and justice is not linear and often proceeds in fits and starts. Many of the issues that existed 50 years ago remain today. A few examples include:
- A 1972 study found that only 5.2% of people employed by the U.S. Department of the Interior in the fields of Earth science and mineral engineering were Black. In 2015, that proportion rose to 5.8% before dipping to 4.9% in 2018, trending opposite the overall demographics of the US workforce. Statistics from the Department of the Interior for the years 2014–2018 are available in this (large) PDF.
- In planetary science, historically excluded groups (e.g., Latinx, Black, Native American) are dramatically underrepresented; according to the 2020 Division of Planetary Sciences workforce survey, Black planetary scientists were underrepresented by 91.6% (i.e., relative to the demographics of the National Civilian Labor Force from the same year, the ratio of the number of Black planetary scientists to the expected number is ~0.08). In historically included groups (i.e., white, Asian American), gender parity remains an issue.
- Even gender-neutral policies — intended to reduce disparities among academics of different genders — can worsen disparities. For example, because of persistent differences in the distribution of childcare responsibilities, men tended to use their parental leave to publish more papers while their teaching and service responsibilities were minimized, while women could not. Thus, even well-intentioned policies can worsen the “leaky pipeline,” forcing people who become pregnant to leave STEM at a disproportionate rate.
To close, the hosts pointed out that despite the immense challenges of the past year, we’ve made some incredible progress as well. To continue to make progress without fizzling out, we need to learn to be allies, practice self-care, sit with discomfort when confronted with complex situations, and live according to our principles, inside and outside of science.
If you’re attending DPS but missed this session, you can check out the slides posted in the #event_wips channel of the DPS 53 Slack workspace or view a recording of the presentation in the virtual DPS meeting space. If you’re interested in the broader issue of equity and justice in planetary science, visit the Women in Planetary Science blog.
Digital illustration of postage stamps featuring the formation of asteroid Psyche. [TAPS Space Travel Gallery, by Brianna Young]
The Art of Planetary Science (by Briley Lewis)
A beloved feature of DPS each year is The Art of Planetary Science (TAPS), a public gallery event run by University of Arizona’s Lunar and Planetary Laboratory. Founded in 2013 by graduate students as an outreach project, TAPS “celebrates the beauty and elegance of science.” Last year, they proudly showed over 200 pieces of art from almost 100 artists and scientists, drawing over 700 guests. Since the conference is virtual this year, the gallery is as well, making it accessible to a wide audience beyond DPS attendees. There are hundreds of artworks in a variety of media, sorted into five categories: Fine Art, Data Art, Space Travel, Kids’ Art, and Space Shorts (short stories or writing entries). The art of this show truly demonstrates the breadth of creativity, including a wide range of different art forms beyond drawing and painting: pottery, music, comics, embroidery, makeup, rugs, spoken word poetry, animated plots, clothing, collage, jewelry, origami, and more!
This year’s 1st place winners feature Mars, meteorites, and even a fictional planet named Bazorp. The Fine Art winner illustrates a human figure near a Martian surface feature known as a draa, a large sandy dune, as imaged by the Mars Reconnaissance Orbiter. The Space Travel winner takes a more abstract approach, imagining a series of hands reaching towards the cosmos. Planet Bazorp makes its appearance in the Kids’ section winner, wherein the artist imagines herself on the distant planet, searching for her long lost friendship bracelet alongside an “alien sloth” and an “alien cheetah.” The writing winner tackles another fun topic, too — space cowboys.
Arguably the most unique category at TAPS, though, is the Data Art collection. Using real images and numerical data, this collection emphasizes the beauty and elegance of a good data visualization tool, as well as creative ways of using real data. This year’s Data Art winner is a gorgeous reconstruction of a meteorite under a microscope, using layers of paper, in the shape of the Antarctic continent where it was discovered. Other entries include simulated orbits of objects in resonance with Neptune, a soundscape based on cosmic ray and solar wind data, and digital art based on Kepler data.
Be sure to check out the gallery, which will be up all week, and vote for the DPS Choice Award and People’s Choice Award. If you’re interested in submitting art for next year’s show, you can join their mailing list to hear the next call for submissions, or follow them on Twitter, YouTube, Facebook, or Instagram!
Tuesday Press Conference (by Sabina Sagynbayeva)
Col-OSSOS: The BrightIR and FaintIR Taxonomy for Kuiper Belt Objects: Wesley Fraser (Herzberg Astronomy and Astrophysics Research Centre)
The first to open today’s press conference is Dr. Wesley Fraser from Herzberg Astronomy and Astrophysics Research Centre, who spoke about Col-OSSOS, the Colours of the Outer Solar System Origins Survey. The aim of this project is to investigate the colors of a large sample of Kuiper Belt Objects and set their taxonomic classification. The unusual tilted and eccentric orbits of KBOs have provided evidence for migration of giant planets in early protoplanetary disk. Astronomers tend to classify the KBOs based on their orbits and composition. Apparently, the variety of such structures is the result of the dynamical processes experienced by KBOs during the dispersal of the early disk. It also has been demonstrated that most equal-sized objects share similar colors, suggesting they have a similar composition. This is where color classification comes in. The result of this work showed that the composition of surfaces is quite homogenous. The color homogeneity of binary pairs contrasts with the overall diversity of colors in the Kuiper belt, which was interpreted as evidence that these KBOs formed from a locally homogeneous and globally heterogeneous protoplanetary disk.
Possible Connections Between an Unusual Micrometeorite and Dwarf Planet Ceres: Maitrayee Bose (Arizona State University)
Next up is Maitrayee Bose, a professor at Arizona State University. Her group found an unusual micrometeorite that’s similar to the dwarf planet Ceres. Micrometeorites are cosmic dust that sometimes rains down on us, produced by both asteroids and comets. These micrometeorites were collected in Antarctica, where they were trapped within cracks in the bedrock. The rare micrometeorite in question, TAM19B-7, doesn’t belong to any known classes of meteorites or micrometeorites, so the researchers decided to look for carbon. Carbon-enriched objects also indicate that they have carbonates and clay, which are formed from interaction with water. They found that TAM19B-7 indeed has a lot more carbon than most other meteorites and micrometeorites! The only meteorite that has the same amount of carbon is Tagish Lake. This carbonate abundance reminded them of Ceres, since its surface has clay and carbonates as well. Maybe TAM19B-7 does have some connection to Ceres! Press release
Lightcurve Observations in Support of the DART Mission: Understanding the Orbit of the Didymos-Dimorphos System: Cristina Thomas (Northern Arizona University)
The upcoming DART mission, launching in November 2021, will target the binary asteroid system Didymos–Dimorphos. The key goal of this mission is to fire an impactor into the smaller asteroid, Dimorphos, and then to measure the change produced in the binary orbital period and characterize the impact site and dynamics. To prepare for the mission, they look at dips in the amount of light observed every time when Dimorphos passes by Didymos (same as looking at the transits of exoplanets!). This information is known as a light curve, which contains the information about “mutual events” that occur when the objects shadow or pass in front of each other, as well as about the rotational periods of Didymos–Dimorphos system. Past analysis of data from 2003 to 2019 found orbital solutions for the binary with an uncertainty on the position of Dimorphos at the time of impact of ± 65 degrees, not very good for targeting the asteroid with a spacecraft. The addition of 2020–2021 data, though, reduced the uncertainty to a much better ± 10 degrees! They now know the orbital period of Dimorphos to within 0.1 second. This new information will help ensure the success of the DART mission. Press release
The Exotic Atmosphere of an Extreme World: Detection of Ionized Calcium in WASP-76b: Emily Deibert (University of Toronto) and Jake Turner (Cornell University)
The collaboration from ExoGemS Survey (Exoplanets with Gemini Spectroscopy) is trying to explore the diversity of exoplanet atmospheres at high resolution from sub-Neptunes to ultra-hot Jupiters, hoping to observe up to 30 planets over the course of the next three years. They want to learn about these planets’ atmospheric compositions, the density and composition of the exoplanet bodies, whether the planets have clouds and winds, etc. Today, Emily Deibert and Jake Turner presented a new discovery within the atmosphere of one of these exoplanets: WASP-76b, a tidally locked ultra-hot Jupiter. Its temperature is about 4400°F! Previous studies indicate that it may rain iron from its skies — and the collaboration has also detected sodium and calcium in its atmosphere. This indicates that the exoplanet is hotter than expected and might have strong atmospheric winds! This discovery was also detected independently by a collaboration Spain as well, so they are pretty certain about their results. Exoplanet atmospheres are even more extreme than previously anticipated! Cornell U. press release | U. of Toronto press release | Queen’s U. Belfast press release
The DPS 53 Exoplanet Panel. [DPS]
Exoplanets Plenary (by Ali Crisp)
This year’s Exoplanets Plenary focused primarily on exoplanet atmospheres, with talks by Drs. Johanna Teske, Laura Schaefer, James Owen, Hilke Schlichting, and Myriam Telus. The talk was moderated by Dr. Jessie Christiansen and Dr. Prabal Saxena. The plenary consisted of five lightning talks from the panel and a Q&A session with the audience.
First up was Dr. Joanna Teske from the Carnegie Institute for Science. Dr. Teske gave an overview of super-Earths, sub-Neptunes, and terrestrial planets, and the current theories of their formation and composition. She also briefly discussed the information we would like to obtain using the composition of exoplanets’ host stars, which might tell us something about planetary atmospheres (though she noted that there isn’t necessarily a direct relationship between stellar composition and planetary composition, since planetary compositions could also be affected by collisions between protoplanets). She ended with an overview of the exciting exoplanet atmosphere science that will come with the launch of JWST.
Then, we had Laura Schaefer from Stanford discussing her work studying outgassing models in the Trappist-1 system. Dr. Schaefer’s research focused on modeling different rates of outgassing from the planetary interiors and the oxidation of the planets’ mantles, and how those rates correlated with atmospheric composition over time. By varying the amount of water vapor in the planetary core models they used, Dr. Schaefer and collaborators were able to model the observed properties of Trappist-1 d, e, and f very well. This work can be used to further model and understand other systems like Trappist-1.
Next up was James Owen from Imperial College London. Dr. Owen presented on models of photoevaporation — in this context, the process of an exoplanet’s atmosphere being blown off by high-energy photons from their host star. He noted that, since photoevaporation requires high energy, it likely would have occurred early in the systems’ lifetimes when their host stars were still more active in the UV and X-ray, meaning that the older exoplanet populations we observe now have already gone through this process. Importantly, the models fit the currently observed radius distribution well, and they could explain the radius gap observed in planets of about two Earth radii.
Hilke Schlichting from UCLA then discussed her research on core-powered mass loss, the process through which the interior cooling of the planet during formation and the resulting gas outflows can cause atmospheric loss. She poses this as an alternative explanation for the radius valley, especially in models where atmospheric loss occurs over a period of 0.5–1 billion years. Further, she discusses two different scenarios that her team was able to determine from their models: reactive and unreactive core models, referring to whether iron was allowed to chemically interact with the planetary atmospheres in the models. They find that the reactive models lead to under-dense planetary cores, which are consistent with observations, but unreactive models do not.
The lightning rounds wrapped up with Myriam Telus from UC Santa Cruz. Dr. Telus discussed an interdisciplinary project she and her graduate student, Maggie Thompson, are working on that focuses on meteorite outgassing and the effects it may have on planetary composition. Essentially, meteorites can be used as a compositional analog for planetesimals during planetary formation in a protoplanetary disk. Seeing what gases they give off when heated in the disk can help us understand the composition of the disk and potentially of exoplanet atmospheres.
If you’re attending DPS and couldn’t make the plenary, Dr. Teske, Dr. Owen, and Dr. Schaefer have all posted their summary slides in the DPS 53 Slack workspace (#200_exoplanets_plenary). The pre-recorded talks are up on the Tuesday tab, and a recording of the session should be posted sometime Wednesday. Discussion will continue in the Slack workspace until the conference ends.