Fixing the thriller of frost hiding on Mars

Martian floor frost, made up largely of carbon dioxide, seems blueish-white in these photographs from the Thermal Emission Imaging System (THEMIS) digital camera aboard NASA’s 2001 Odyssey orbiter. THEMIS takes photographs in each seen gentle perceptible to the human eye and heat-sensitive infrared. Credit score: NASA/JPL-Caltech/ASU

A brand new examine utilizing information from NASA’s Mars Odyssey orbiter might clarify why Martian frost could be invisible to the bare eye and why mud avalanches seem on some slopes.

Scientists have been baffled final yr when learning photographs of the Martian floor taken at daybreak by NASA’s Mars Odyssey orbiter. Once they seemed on the floor utilizing seen gentle—the type that the human eye perceives—they may see ghostly, blue-white morning frost illuminated by the rising solar. However utilizing the orbiter’s heat-sensitive digital camera, the frost appeared extra broadly, together with in areas the place none was seen.

The scientists knew they have been taking a look at frost that kinds in a single day and is made largely of carbon dioxide—primarily, dry ice, which frequently seems as frost on the Pink Planet reasonably than as water ice. However why was this dry ice frost seen in some locations and never others?

In a paper printed final month within the Journal of Geophysical Analysis: Planets, these scientists proposed a shocking reply which will additionally clarify how mud avalanches, that are reshaping the planet, are triggered after dawn.

From frost to vapor

Launched in 2001, Odyssey is NASA’s longest-lived Mars mission and carries the Thermal Emission Imaging System (THEMIS), an infrared, or temperature-sensitive, digital camera that gives a one-of-a-kind view of the Martian floor. Odyssey’s present orbit supplies a singular take a look at the planet at 7 a.m. native Mars time.

Science at sunrise: Solving the mystery of frost hiding on Mars
These darkish streaks, also referred to as “slope streaks,” resulted from mud avalanches on Mars. The HiRISE digital camera aboard NASA’s Mars Reconnaissance Orbiter captured them on Dec. 26, 2017. Credit score: NASA/JPL-Caltech/UArizona

“Odyssey’s morning orbit produces spectacular photos,” mentioned Sylvain Piqueux of NASA’s Jet Propulsion Laboratory in Southern California, who led the paper. “We are able to see the lengthy shadows of dawn as they stretch throughout the floor.”

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As a result of Mars has so little environment (simply 1% the density of Earth’s), the solar rapidly warms frost that builds up in a single day. As a substitute of melting, dry ice vaporizes into the environment inside minutes.

Lucas Lange, a JPL intern working with Piqueux, first observed the cold-temperature signature of frost in lots of locations the place it couldn’t be seen on the floor. These temperatures have been showing simply tens of microns underground—lower than the width of a human hair “under” the floor.

“Our first thought was ice might be buried there,” Lange mentioned. “Dry ice is plentiful close to Mars’ poles, however we have been wanting nearer to the equator of the planet, the place it’s usually too heat for dry ice frost to type.”

Of their paper, the authors suggest they have been seeing “soiled frost”—dry ice frost combined with superb grains of mud that obscured it in seen gentle however not in infrared photographs.

Thawing frost and avalanches

The phenomenon led the scientists to suspect soiled frost may also clarify among the darkish streaks that may stretch 3,300 toes (1,000 meters) or extra down Martian slopes. They knew the streaks resulted from, primarily, mud avalanches that slowly reshape mountainsides throughout the planet. Scientists suppose these mud avalanches most likely look one thing like a ground-hugging river of mud releasing a path of fluffy materials behind. Because the mud travels downhill over a number of hours, it exposes streaks of darker materials beneath.

Science at sunrise: Solving the mystery of frost hiding on Mars
These darkish streaks, also referred to as “slope streaks,” resulted from mud avalanches in an space of Mars referred to as Acheron Fossae. The HiRISE digital camera aboard NASA’s Mars Reconnaissance Orbiter captured them on Dec. 3, 2006. Credit score: NASA/JPL-Caltech/UArizona

These darkish streaks aren’t the identical as a better-documented selection referred to as recurring slope lineae, which recur in the identical locations, season after season, for weeks (as an alternative of hours) at a time. As soon as thought to outcome from briny water slowly seeping from mountainsides, recurring slope lineae at the moment are usually believed to outcome from flows of dry sand or mud.

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Mapping the slopes streaks for his or her current examine, the authors discovered they have an inclination to seem in locations with morning frost. The researchers suggest the streaks resulted from the vaporizing frost creating simply sufficient strain to loosen the mud grains, inflicting an avalanche.

The hypotheses are additional proof of simply how shocking the Pink Planet could be.

“Each time we ship a mission to Mars, we uncover unique new processes,” mentioned Chris Edwards, a paper co-author at Northern Arizona College in Flagstaff. “We don’t have something precisely like a slope streak on Earth. You must suppose past your experiences on Earth to grasp Mars.”


It’s springtime on Mars, and the dunes are defrosting


Extra info:
L. Lange et al, Gardening of the Martian Regolith by Diurnal CO 2 Frost and the Formation of Slope Streaks, Journal of Geophysical Analysis: Planets (2022). DOI: 10.1029/2021JE006988
Supplied by
Jet Propulsion Laboratory

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Fixing the thriller of frost hiding on Mars (2022, Might 5)
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