New global images of Mars from NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission being led by CU Boulder show the ultraviolet glow from the Martian atmosphere in unprecedented detail, revealing dynamic, previously invisible behavior. They include the first images of “nightglow” that can be used to show how winds circulate at high altitudes. Additionally, dayside ultraviolet imagery from the spacecraft shows how ozone amounts change over the seasons and how afternoon clouds form over giant Martian volcanoes. The images were taken by the Imaging UltraViolet Spectrograph (IUVS) on MAVEN.
“MAVEN obtained hundreds of such images in recent months, giving some of the best high-resolution ultraviolet coverage of Mars ever obtained,” said CU Boulder Professor Nick Schneider of the Laboratory for Atmospheric and Space Physics (LASP). Schneider is presenting new MAVEN results Oct. 19 at the American Astronomical Society Division for Planetary Sciences meeting in Pasadena, California.
CU Boulder designed and built the IUVS instrument and the Langmuir Probe and Waves experiment for the MAVEN mission. CU Boulder Professor Bruce Jakosky of LASP is the mission’s principal investigator and the university is leading science operations as well as public education and outreach for the mission.
Nightside images show ultraviolet (UV) “nightglow” emission from nitric oxide (abbreviated NO). Nightglow is a common planetary phenomenon in which the sky faintly glows even in the complete absence of external light. The “nightside” atmosphere of Mars emits light in the ultraviolet due to chemical reactions that start on its dayside.
Ultraviolet light from the sun breaks down molecules of carbon dioxide and nitrogen, and the resulting atoms are carried around the planet by high-altitude wind patterns that encircle the planet. On the nightside, these winds bring the atoms down to lower altitudes where nitrogen and oxygen atoms collide to form nitric oxide molecules. The recombination releases extra energy, which comes out as ultraviolet light.
Scientists predicted NO nightglow at Mars, and prior missions detected its presence, but MAVEN has returned the first images of this phenomenon in the Martian atmosphere. Splotches and streaks appearing in these images occur where NO recombination is enhanced by winds. Such concentrations are clear evidence of strong irregularities in high altitude winds and circulation patterns on Mars.
These winds control how the Red Planet’s atmosphere responds to its very strong seasonal cycles. These first images will lead to an improved determination of the circulation patterns that control the behavior of the atmosphere from approximately 37 to 62 miles (about 60 to 100 kilometers) high.
Dayside images show the atmosphere and surface near the south pole of Mars in unprecedented ultraviolet detail. They were obtained as spring comes to the southern hemisphere. Ozone is destroyed when water vapor is present, so ozone accumulates in the winter polar region where the water vapor has frozen out of the atmosphere.
The images show ozone lasting into spring, indicating that global winds are inhibiting the spread of water vapor from the rest of the planet into winter polar regions. Wave patterns in the images, revealed by UV absorption from ozone concentrations, are critical to understanding the wind patterns, giving scientists an additional means to study the chemistry and global circulation of the atmosphere.
MAVEN observations also show afternoon cloud formation over the four giant volcanoes on Mars, much as clouds form over mountain ranges on Earth. The tallest, Olympus Mons is 88,000 feet, more than three times the height of Mt. Everest.
IUVS images of cloud formation are among the best ever taken showing the development of clouds throughout the day. Clouds are a key to understanding a planet's energy balance and water vapor inventory, so these observations will be valuable in understanding the daily and seasonal behavior of the atmosphere.
“Clouds form on every planet in our solar system with enough atmosphere, often involving conditions or ingredients not found on Earth,” said Schneider. “But these Mars clouds, forming over tall mountains in the afternoon, are surprisingly familiar,” said Schneider. “People think of Mars as completely unlike Earth, but these scenes of afternoon cloud buildup over the mountains remind me of Colorado.”
“MAVEN's elliptical orbit is just right,” said CU Boulder Research Associate Justin Deighan of LASP, who led the observations. “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.”
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN project and provided two science instruments for the mission. The University of California at Berkeley’s Space Sciences Laboratory also provided four science instruments for the mission. Lockheed Martin built the spacecraft and is responsible for mission operations. NASA’s Jet Propulsion Laboratory in Pasadena, California, provides navigation and Deep Space Network support, as well as the Electra telecommunications relay hardware and operations.