Thanasis Economou, Senior Scientist at Chicago's Enrico Fermi Institute, suggested the new study after observing that the APXS instruments aboard NASA's twin Mars rovers, Spirit and Opportunity, had recorded fluctuations in the argon composition of the Martian atmosphere. "The amount of argon in the atmosphere is changing constantly," Economou said.
During warmer seasons, approximately 95 percent of the Martian atmosphere consists of carbon dioxide. Nitrogen accounts for almost 3 percent and argon for less than 2 percent. But when winter sets in at one of the poles, carbon dioxide freezes out of the atmosphere to form a polar cap, causing a low-pressure system that moves air toward the pole.
Argon stays in the atmosphere and becomes enhanced because it freezes at a much lower temperature, Economou said. An instrument on NASA's Odyssey orbiter around Mars found that on the Mars south pole during the winter, the argon concentration is six times higher than during the warmer seasons.
"The amount of argon that comes with the air mass stays in the atmosphere," he explained. "Carbon dioxide drops, so the ratio of argon to carbon dioxide is increasing constantly until the next season."
With the onset of warmer spring and summer temperatures, the frozen carbon dioxide evaporates back into the atmosphere, causing a high-pressure system that pushes the air mass back toward the equator.
"The fact that we see a signal at all means there's a lot of mixing between the polar air and the air at the tropics," said Ray Pierrehumbert, the Louis Block Professor in Geophysical Sciences at the University of Chicago, who specializes in the evolution of climate on Earth and Mars. "It gives you a way of inferring aspects of the Martian circulation that you can't observe at all with any other instrument that's out there," he said.
Scientists are coupling the APXS measurements with additional data collected by the orbiting Mars Odyssey spacecraft. The APXS measures the number of argon atoms at the rover's location between the instrument and the ground-a distance of a couple of centimeters (a few inches). Odyssey's gamma-ray spectrometer, meanwhile, measures the argon in a column of air extending from the upper atmosphere to the Martian surface, but over an area spanning several hundred kilometers (a couple hundred miles)
Spirit and Opportunity landed on Mars in January 2004. Until now, their APXS instruments have focused on measuring the chemical content of rocks and dust sitting on the ground. During the mission's first 90 days, for example, Opportunity's APXS contributed to the identification and analysis of abundant sulfate salts and other minerals suggestive of once-moist environments on the vast plain known as Meridiani Planum.
"It means that at some point the site was soaked with liquid water," Economou said.
Opportunity's APXS also performed a key analysis of the first meteorite ever discovered on Mars. When Opportunity encountered Heat Shield rock in 2005, "it looked like a meteorite, but it was confirmed with the APXS," Economou said. It was the first of at least four meteorites that Opportunity has discovered.
"If you go to Antarctica you find lots of them because you can spot them," he said. "On Mars also, when you have these large, flat areas that have just sand and sand dunes, nothing else, and you now see some suspicious rock, you know that it's not from there." Either it is debris that has been ejected from an impact crater, or a meteorite.
In recent months, the APXS on the Spirit rover measured the composition of soils consisting of 90 percent pure silica, which could have formed in a hot-spring environment or some other process involving water. The finding presents some of the best evidence yet that water once existed at Gusev crater.
"This is a remarkable discovery," said Cornell University's Steve Squyres, who heads the Mars rovers' science instruments team. "The fact that we found something this new and different after nearly 1,200 days on Mars makes it even more remarkable. It makes you wonder what else is still out there."
Opportunity now has traveled more than six miles through some difficult sandy terrain to reach Victoria Crater, which measures half a mile in diameter. Rolling up to the edge of the crater, the rover has taken images of the layered sediments, various rock types and accumulations of sand visible at the base of the walls.
NASA engineers have scouted a possible route that Opportunity could safely follow onto the crater floor. A dust storm in the region has delayed plans to send Opportunity into the crater.
"This is a magnificent crater with a lot of exposed bedrocks and walls showing geologic detail with extensive layering that makes the team geologist very happy," Economou said. "What you can see is amazing."
Space radiation won't stop NASA's human exploration
18.10.2017 | NASA/Johnson Space Center
Study shows how water could have flowed on 'cold and icy' ancient Mars
18.10.2017 | Brown University
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
18.10.2017 | Materials Sciences
18.10.2017 | Physics and Astronomy
18.10.2017 | Physics and Astronomy