From UC Santa Cruz : “Baked meteorites yield clues to planetary atmospheres”

From UC Santa Cruz

April 15, 2021
Tim Stephens
stephens@ucsc.edu

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The early atmospheres of rocky planets are thought to form mostly from gases released from the surface of the planet as a result of the intense heating during the accretion of planetary building blocks and later volcanic activity early in the planet’s development. (Illustration by Dan Durda/ Southwest Research Institute (US))

In a novel laboratory investigation of the initial atmospheres of Earth-like rocky planets, researchers at UC Santa Cruz heated pristine meteorite samples in a high-temperature furnace and analyzed the gases released.

Their results, published April 15 in Nature Astronomy, suggest that the initial atmospheres of terrestrial planets may differ significantly from many of the common assumptions used in theoretical models of planetary atmospheres.

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Samples from three carbonaceous chondrite meteorites—Murchison, Jbilet Winselwan, and Aguas Zarcas—were analyzed in the outgassing experiments. Credit: M. Thompson)

“This information will be important when we start being able to observe exoplanet atmospheres with new telescopes and advanced instrumentation,” said first author Maggie Thompson, a graduate student in astronomy and astrophysics at UC Santa Cruz.

The early atmospheres of rocky planets are thought to form mostly from gases released from the surface of the planet as a result of the intense heating during the accretion of planetary building blocks and later volcanic activity early in the planet’s development.

“When the building blocks of a planet are coming together, the material is heated and gases are produced, and if the planet is large enough the gases will be retained as an atmosphere,” explained coauthor Myriam Telus, assistant professor of Earth and planetary sciences at UC Santa Cruz. “We’re trying to simulate in the laboratory this very early process when a planet’s atmosphere is forming so we can put some experimental constraints on that story.”

The researchers analyzed three meteorites of a type known as CM-type carbonaceous chondrites, which have a composition considered representative of the material from which the sun and planets formed.

“These meteorites are left over materials from the building blocks that went into forming the planets in our solar system,” Thompson said. “Chondrites are different from other types of meteorites in that they didn’t get hot enough to melt, so they have held onto some of the more primitive components that can tell us about the composition of the solar system around the time of planet formation.”

Working with materials scientists in the physics department, the researchers set up a furnace connected to a mass spectrometer and a vacuum system. As the meteorite samples were heated to 1200 degrees Celsius, the system analyzed the volatile gases produced from the minerals in the sample. Water vapor was the dominant gas, with significant amounts of carbon monoxide and carbon dioxide, and smaller amounts of hydrogen and hydrogen sulfide gases also released.

According to Telus, models of planetary atmospheres often assume solar abundances—that is, a composition similar to the sun and therefore dominated by hydrogen and helium.

“Based on outgassing from meteorites, however, you would expect water vapor to be the dominant gas, followed by carbon monoxide and carbon dioxide,” she said. “Using solar abundances is fine for large, Jupiter-size planets that acquire their atmospheres from the solar nebula, but smaller planets are thought to get their atmospheres more from outgassing.”

The researchers compared their results with the predictions from chemical equilibrium models based on the composition of the meteorites. “Qualitatively, we get pretty similar results to what the chemical equilibrium models predict should be outgassed, but there are also some differences,” Thompson said. “You need experiments to see what actually happens in practice. We want to do this for a wide variety of meteorites to provide better constraints for the theoretical models of exoplanetary atmospheres.”

Other researchers have done heating experiments with meteorites, but those studies were for other purposes and used different methods. “A lot of people are interested in what happens when meteorites enter Earth’s atmosphere, so those kinds of studies were not done with this framework in mind to understand outgassing,” Thompson said.

The three meteorites analyzed for this study were the Murchison chondrite which fell in Australia in 1969; Jbilet Winselwan, collected in Western Sahara in 2013; and Aguas Zarcas, which fell in Costa Rica in 2019.

“It may seem arbitrary to use meteorites from our solar system to understand exoplanets around other stars, but studies of other stars are finding that this type of material is actually pretty common around other stars,” Telus noted.

The investigation brought together researchers from three departments at UCSC: Astronomy and Astrophysics, Earth and Planetary Sciences, and Physics. In addition to Thompson and Telus, the coauthors of the paper include astrophysicist Jonathan Fortney and physicists Toyanath Joshi and David Lederman at UC Santa Cruz, and Laura Schaefer at Stanford University (US). This research was supported by National Aeronautics and Space Administration(US) and the ARCS Foundation.

See the full article here .


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UC Santa Cruz (US) Lick Observatory | Since 1888, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)

UC Observatories Lick Automated Planet Finder, fully robotic 2.4-meter optical telescope at Lick Observatory, situated on the summit of Mount Hamilton, east of San Jose, California, USA.

The UCO Lick C. Donald Shane telescope is a 120-inch (3.0-meter) reflecting telescope located at the Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft).

The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

UCSC is the home base for the Lick Observatory.

UCO Lick Observatory‘s 36-inch Great Refractor telescope housed in the South (large) Dome of main building.

Search for extraterrestrial intelligence expands at Lick Observatory
New instrument scans the sky for pulses of infrared light
March 23, 2015
By Hilary Lebow

The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch)

Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

UC Santa Cruz (US) alumna Shelley Wright, now an assistant professor of physics at UC San Diego (US), discusses the dichroic filter of the NIROSETI instrument, developed at the U Toronto Dunlap Institute for Astronomy and Astrophysics (CA) and brought to UCSD and installed at the UC Santa Cruz (US) Lick Observatory Nickel Telescope (Photo by Laurie Hatch).

“Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego (US) who led the development of the new instrument while at the U Toronto Dunlap Institute for Astronomy and Astrophysics (CA).

Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

Frank Drake with his Drake Equation. Credit Frank Drake.

“The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

“We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

“This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

“Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.