"Mars either has more gusts of wind than we knew about before, or the winds are capable of transporting more sand," said Nathan Bridges, planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., and lead author of a paper on the finding published online this month in the journal Geology. "We used to think of the sand on Mars as relatively immobile, so these new observations are changing our whole perspective."
While red dust is known to swirl all around Mars in storms and dust devils, the planet's dark sand grains are larger and harder to move. Less than a decade ago, scientists thought the dunes and ripples on Mars either did not budge or moved too slowly for detection.
MRO was launched in 2005. Initial images from the spacecraft's High Resolution Imaging Science Experiment (HiRISE) camera documented only a few cases of shifting sand dunes and ripples, collectively called bedforms. Now, after years of monitoring the Martian surface, the spacecraft has documented movements of a few yards (or meters) per year in dozens of locations across the planet.
The air on Mars is thin, so stronger gusts of wind are needed to push a grain of sand. Wind-tunnel experiments have shown that a patch of sand would take winds of about 80 mph (nearly 130 kilometers per hour) to move on Mars compared with only 10 mph (about 16 kilometers per hour) on Earth. Measurements from the meteorology experiments on NASA's Viking landers in the 1970s and early 1980s, in addition to climate models, showed such winds should be rare on Mars.
The first hints that Martian dunes move came from NASA's Mars Global Surveyor, which operated from 1997 to 2006. But the spacecraft's cameras lacked the resolution to definitively detect the changes. NASA's Mars Exploration Rovers also detected hints of shifting sand when they touched down on the Red Planet's surface in 2004. The mission team was surprised to see grains of sand dotting the rovers' solar panels. They also witnessed the rovers' track marks filling in with sand.
"Sand moves by hopping from place to place," said Matthew Golombek, a co-author of the new paper and a member of the Mars Exploration Rover and Mars Reconnaissance Orbiter teams at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Before the rovers landed on Mars, we had no clear evidence of sand moving."
Not all of the sand on Mars is blowing in the wind. The study also identifies several areas where the bedforms did not move.
"The sand dunes where we didn't see movement today could have larger grains, or perhaps their surface layers are cemented together," said Bridges, who also is a member of the HiRISE team. "These studies show the benefit of long-term monitoring at high resolution."
According to scientists, the seemingly stationary areas might move on much larger time scales, triggered by climate cycles on Mars that last tens of thousands of years. The tilt of Mars' axis relative to its orbital plane can vary dramatically. This, combined with the oval shape of Mars' orbit, can cause extreme changes in the Martian climate, much greater than those experienced on Earth. Mars may once have been warm enough that the carbon dioxide now frozen in the polar ice caps could have been free to form a thicker atmosphere, leading to stronger winds capable of transporting sand.
HiRISE, one of six instruments on the Mars Reconnaissance Orbiter, is operated by the University of Arizona in Tucson. The instrument was built by Ball Aerospace & Technologies Corp. of Boulder, Colo. APL provided and operates the MRO’s Compact Reconnaissance Imaging Spectrometer (CRISM). The Mars Exploration Rovers Opportunity and Spirit were built by JPL. JPL also manages the MRO and Mars Exploration Rover projects for NASA's Science Mission Directorate in Washington. MRO images and additional information are available online at http://www.nasa.gov/MRO. For more information about NASA Mars missions, visit the Web at: www.nasa.gov/mars.
The Applied Physics Laboratory, a not-for-profit division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit www.jhuapl.edu.
Geoffrey Brown | Newswise Science News
Basque researchers turn light upside down
23.02.2018 | Elhuyar Fundazioa
Attoseconds break into atomic interior
23.02.2018 | Max-Planck-Institut für Quantenoptik
A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.
In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...
A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.
By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
23.02.2018 | Physics and Astronomy
23.02.2018 | Health and Medicine
23.02.2018 | Physics and Astronomy