. Space Travel News .




.
MARSDAILY
A glow in the Martian night throws light on atmospheric circulation
by Staff Writers
Paris (ESA) Mar 27, 2012

The OMEGA instrument on Mars Express has detected oxygen emission at the night side of Mars. The emission, at a wavelength of 1.27 m, was detected on three occasions during a series of 40 observations made by OMEGA above the planet's limb. The panels above show, from left to right: a 2.2 degrees wide swath of the observed limb at night with emission coded in pink; the vertical distribution of the intensity observed in megaRayleigh (MR) - integration over azimuth. The red line is a smoothed version of the distribution; the integrated observed spectrum, showing emission only at 1.27 m. Copyright: Image courtesy of Bertaux, J.-L., et al. (2012).

A faint, infrared glow above the winter poles of Mars is giving new insights into seasonal changes in the planet's atmospheric circulation. The tell-tale night emission was first detected in 2004 in observations made by the OMEGA imaging spectrometer on ESA's Mars Express orbiter.

Writing in a recent issue of the Journal of Geophysical Research, a team of French scientists reported on the first detection of an infrared emission above the polar regions of Mars. The emission, at a wavelength of 1.27 microns, was detected on three occasions (in 2004, 2005 and 2006) during a series of 40 observations made by OMEGA above the planet's limb.

Infrared emissions are not unusual in planetary atmospheres. In the upper atmospheres of both Venus and Mars, carbon dioxide (CO2) and nitrogen (N2) molecules are split or photodissociated by solar ultraviolet (UV) light. This produces oxygen and nitrogen atoms in the region known as the thermosphere, at an altitude of about 80-90 km above each planet's dayside.

Spacecraft observations show that the thermospheric circulation of Venus is characterised by a strong flow of air from the warmer, sub-solar point (local midday) toward the anti-solar point (local midnight). The cooler gas on the night side then begins to descend.

As the sinking gas comes into contact with carbon dioxide molecules in the atmosphere, the atoms of oxygen and nitrogen recombine. This recombination process results in an ultraviolet nightglow from nitric oxide (NO), as well as a near-infrared oxygen (O2) emission at 1.27 microns.

A comparable NO emission in the atmosphere of Mars was detected by the SPICAM instrument on Mars Express in 2005. Since this was also attributed to atmospheric circulation, scientists expected to see the associated O2 emission, but the nighttime glow from excited molecular oxygen was not confirmed until the OMEGA observations first reported in 2010.

"We think that the faintness of the infrared oxygen emission over the nightside of Mars may result from the slower descent of the cold air - which means less recombination of the oxygen atoms - and a less intense bombardment by solar UV light, which reduces the rate of photodissociation," explained Jean-Loup Bertaux from LATMOS / Universite de Versailles Saint-Quentin, who was lead author of the paper.

The authors believe that the natural light emissions from the atmosphere are clearly associated with the planet's atmospheric circulation. Although few direct observations of Martian high level winds have been made, it is believed that air rises above the warmer, summer pole, moves across the equator and then descends near the winter pole, on the planet's night side. This circulation apparently takes the form of a simple Hadley cell, very much like the atmospheric motion which occurs on either side of Earth's equator.

As predicted by general circulation models of Mars, all of the OMEGA oxygen nightglow observations were obtained at high latitudes, during the winter night. This location coincides with the region where cooler gas is sinking above the pole which is experiencing long-term darkness - similar to the winter pole on Earth.

"When exposed to solar UV radiation above an altitude of 70 km, carbon dioxide molecules - the main atmospheric constituent of Mars' atmosphere - are split into carbon monoxide and oxygen atoms," said Jean-Loup Bertaux.

"Those oxygen atoms are transported by a gigantic Hadley cell, which features an ascending branch above the daytime summer pole and a descending branch over the winter pole, which is in the night hemisphere. The oxygen atoms recombine into molecular oxygen in the descending branch of the Hadley cell, at an altitude of 30-50 km."

Further observations are required to confirm what happens around the time of the Martian equinoxes, when the Sun is overhead at the equator and neither pole is in darkness. Around those dates, the OMEGA data and the general circulation model show that a different pattern establishes, with two symmetrical Hadley cells. Air rises near the equator, and divides into two branches, one going north and the other going south, with air descending simultaneously over both poles.

The paper also addresses whether OMEGA nightglow observations may help to solve the mystery of Martian methane. Although it is easily destroyed by solar UV, the gas is still present on the red planet today.

The authors consider the impact of Hadley circulation on the long-term stability of methane and conclude that recycling of the atmosphere at high altitude seems far too slow to significantly decrease the lifetime of the gas near the surface.

"These findings provide important constraints on the overall aeronomy and atmospheric dynamics of Mars," said Olivier Witasse, ESA's project scientist for Mars Express. "They should also stimulate research into Earth's atmosphere, through comparisons of the processes influencing the global circulations of the two neighbouring planets."

Reference publications:
Bertaux, J.-L., et al., "First detection of O2 1.27 m nightglow emission at Mars with OMEGA/MEX and comparison with general circulation model predictions", J. Geophys. Res., 117, E00J04, 2012. doi:10.1029/2011JE003890.

Gondet, B., et al., "O2 nightglow emission detected in Mars atmosphere by OMEGA/Mars Express", paper presented at the European Geosciences Union General Assembly, Vienna, 3 May, 2010.

Clancy, R. T., et al., "CRISM limb observations of O2 singlet delta nightglow in the polar winter atmosphere of Mars", Bull. Am. Astron. Soc., 42, 1041 2010. http://adsabs.harvard.edu/abs/2010DPS....42.4202C

The results described here are based on measurements of O2 emission at 1.27 microns obtained from limb observations with the OMEGA imaging spectrometer on board Mars Express. This emission was detected in observations performed on 22 November 2004, 21 April 2005 and 27 January 2006.

Detections of the oxygen nightglow on Mars with the CRISM instrument on board NASA's Mars Reconnaissance Orbiter have also been reported.

The other scientists involved in this study with OMEGA data are: B. Gondet (IAS-Orsay, France), F. Lefevre (LATMOS/IPSL/UPMC, France), J. P. Bibring (IAS-Orsay, France), and F. Montmessin (LATMOS/IPSL/UVSQ, France).

Related Links
Mars Express at ESA
Mars News and Information at MarsDaily.com
Lunar Dreams and more




.
.
Get Our Free Newsletters Via Email
...
Buy Advertising Editorial Enquiries



And it's 3... 2... 1... blastoff! Discover the thrill of a real-life rocket launch.



.

. Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle



MARSDAILY
Martian Carbon Dioxide Clouds Tied To Atmospheric Gravity Waves
Granada, Spain (SPX) Feb 15, 2012
On 4 March 1997 the Mars Pathfinder lander fell through the thin Martian atmosphere. During its descent, instrumentation aboard the lander recorded the changing atmospheric temperature, pressure, and density. Within this atmospheric profile, researchers identified anomalous cold air packets within the Martian mesosphere (60-90 kilometers, or 37-56 miles, altitude). Later orbital meas ... read more


MARSDAILY
ILS Proton Launches Intelsat 22

US ramping up private sector's role in spaceflight

Europe's smart supply ship on its way to Space Station

Third Ariane 5 ready for launch in 2012

MARSDAILY
A glow in the Martian night throws light on atmospheric circulation

Mars Science Laboratory Adjusts Orbital Path And Tests Instruments

Geologists discover new class of landform - on Mars

Red Food For the Red Planet

MARSDAILY
NASA's Grail MoonKam Returns First Student-Selected Lunar Images

Ecliptic "MoonKAM" Systems Begin Operations in Lunar Orbit

Two New NASA LRO Videos: See Moon's Evolution, Take a Tour

China to get lunar soil

MARSDAILY
New Horizons on Approach: 22 AU Down, Just 10 to Go

MARSDAILY
Runaway Planets Zoom at a Fraction of Light-Speed

Some orbits more popular than others in solar systems

Herschel's new view on giant planet formation

Kepler Statistical Analysis Suggests Earthlike Planets Extremely Rare

MARSDAILY
N. Korea takes rocket main body to launch site

NASA Sub-Scale Solid-Rocket Motor Tests Material for Space Launch System

Pratt and Whitney Rocketdyne Hot-Fires Launch Abort

NASA Sub-Scale Solid-Rocket Motor Tests Material for Space Launch System

MARSDAILY
China's Lunar Docking

Shenzhou-9 may take female astronaut to space

China to launch 100 satellites during 2011-15

Three for Tiangong

MARSDAILY
New NEO Website Tool Now Available

Dawn Sees New Surface Features on Giant Asteroid

Near-miss asteroid will return next year

Dear Ups and Dawns


Memory Foam Mattress Review

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

.

The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement