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MAVEN captures detailed ultraviolet images of Mars’ atmosphere

MAVEN's Imaging UltraViolet Spectrograph images of rapid cloud formation on Mars, July 9-10, 2016

MAVEN’s Imaging UltraViolet Spectrograph obtained these images of rapid cloud formation on Mars on July 9–10, 2016. The ultraviolet colors of the planet have been rendered in false color, to show what we would see with ultraviolet-sensitive eyes. The series interleaves MAVEN images to show about 7 hours of Mars rotation during this period, just over a quarter of Mars’ day. The left part of the planet is in morning and the right side is in afternoon. Mars’ prominent volcanoes, topped with white clouds, can be seen moving across the disk. Mars’ tallest volcano, Olympus Mons, appears as a prominent dark region near the top of the images, with a small white cloud at the summit that grows during the day. Olympus Mons appears dark because the volcano rises up above much of the hazy atmosphere which makes the rest of the planet appear lighter. Three more volcanoes appear in a diagonal row, with their cloud cover merging to span up to a thousand miles by the end of the day. These images are particularly interesting because they show how rapidly and extensively the clouds topping the volcanoes form in the afternoon. Similar processes occur at Earth, with the flow of winds over mountains creating clouds. Afternoon cloud formation is a common occurrence in the American West, especially during the summer. Image & Caption Credit: NASA / MAVEN / University of Colorado

NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has taken hundreds of high-resolution photos of the Red Planet’s atmosphere in ultraviolet light, revealing unprecedented details of its cloud formation and high-altitude wind circulation.

Captured over the last several months by MAVEN’s Imaging UltraViolet Spectrograph (IUVS), the images depicting cloud formation were processed in false color and compiled to create a movie of activity visible only in the ultraviolet.

Photos of the planet’s nightside show the phenomenon known as ultraviolet “nightglow”, in which the nightside of a planet exhibits a faint glow in spite of being in complete darkness.

Image of the Mars' night side in ultraviolet observed by MAVEN

This image of the Mars’ nightside shows ultraviolet emission from nitric oxide (abbreviated NO). The emission is shown in false color with black as low values, green as medium, and white as high. These emissions track the recombination of atomic nitrogen and oxygen produced on the dayside, and reveal the circulation patterns of the atmosphere. The splotches, streaks, and other irregularities in the image are indications that atmospheric patterns are extremely variable on Mars’ nightside. The inset shows the viewing geometry on the planet. MAVEN’s Imaging UltraViolet Spectrograph obtained this image of Mars on May 4, 2016, during late winter in Mars’ Southern Hemisphere. Image & Caption Credit: NASA / MAVEN / University of Colorado

Mars' south pole in ultraviolet observed by MAVEN

Mars’ south pole in ultraviolet observed by MAVEN. (Mouse over for details) Image Credit: NASA / MAVEN / University of Colorado

On Mars, this glow is caused by the emission of nitric oxide (NO) resulting from chemical reactions occurring on the dayside of the planet. There, carbon dioxide and nitrogen molecules are broken down by ultraviolet sunlight, releasing atoms that are then carried around the planet by high-altitude winds.

Once on the nightside, these winds bring the nitrogen and oxygen atoms down to lower altitudes where they subsequently collide with one another in a process that reforms the nitric oxide molecules while releasing excess energy in the form of ultraviolet light.

Ultraviolet dayside images show both the surface and atmosphere of Mars’ south pole in vivid detail. Now entering spring, the south polar region contains deposits of ozone that accumulated during the winter when water vapor froze out of the atmosphere.

Global winds circling the planet are preventing the spread of water vapor from other parts of the planet into the south polar region.

Patterns of planet-wide winds are visible as wave patterns only in the ultraviolet, so these images are providing scientists with a new tool for understanding the Martian atmosphere’s chemistry and wind circulation.

Also visible in the dayside images are clouds forming over Mars’ four huge volcanoes, much like they form over volcanoes on Earth. Photos obtained on July 9–10, 2016, show the evolution of the clouds during a seven-hour period, which constitutes one-quarter of a Martian day.

These photos will play a key role in helping scientists better understand both daily and seasonal changes on the Red Planet because cloud patterns provide vital information about a planet’s water vapor and energy balance.

“MAVEN’s elliptical orbit is just right. It rises high enough to take a global picture, but still orbits fast enough to get multiple views as Mars rotates over the course of a day,” said Justin Deighan, mission observation leader from the University of Boulder, Colorado.

MAVEN ultraviolet image of clouds over Martian volcanoes

MAVEN’s Imaging UltraViolet Spectrograph obtained images of rapid cloud formation on Mars on July 9-10, 2016. The ultraviolet colors of the planet have been rendered in false color, to show what we would see with ultraviolet-sensitive eyes. Mars’ tallest volcano, Olympus Mons, appears as a prominent dark region near the top of the image, with a small white cloud at the summit that grows during the day. Three more volcanoes appear in a diagonal row, with their cloud cover (white areas near center) merging to span up to a thousand miles by the end of the day. Image & Caption Credit: NASA / MAVEN / University of Colorado

The findings are all the more interesting because scientists did not expect to find any nightglow on Mars.

Blotchy areas and streaks in the images indicate Mars’ high-altitude winds have irregular circulation patterns. Because atmospheric responses to seasonal cycles are controlled by these winds, data from these images will be especially useful in helping scientists understand the way the Martian atmosphere behaves between 37 and 62 miles (60-100 km) above the surface.

Video Courtesy of NASA.gov Video

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Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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