Washington, Jan 24 : Scientists have observed new detailed views of the dynamic wind-driven geology of Mars, using The University of Arizona's HiRISE (High Resolution Imaging Experiment) camera.
The HiRISE camera on NASA's Mars Reconnaissance Orbiter, has been able to observe 20-inch-diameter features while flying at about 7,500 mph between 155 and 196 miles above the Martian surface.
According to HiRISE team members, one of the main objectives of the observations is to find if winds on present-day Mars are strong enough to form and change geological features, or if wind-constructed formations were made in the past, perhaps when winds speeds and atmospheric pressures were higher.
"We're seeing what look like smaller sand bedforms on the tops of larger dunes, and, when we zoom in more, a third set of bedforms topping those," said HiRISE co-investigator Nathan Bridges of the Jet Propulsion Laboratory in Pasadena, California.
"Bedforms," or wind-deposited landforms, can be of two types. They can be sand dunes, which are typically larger and have distinct shapes. Or they can be ripples, which is sand mixed with coarser, millimeter-sized particles.
The HiRISE images also show that what covers the slopes of the high Martian volcanoes are definitely dunes or ripples that appear to have an organized 'reticulate' structure possibly formed by winds blowing from multiple directions.
"On Earth, winds blowing from many different directions form what are called 'star dunes,' and these look somewhat like those," said Bridges. "The reticulate surface looks like a network of connected wind-blown dunes and ripples," he explained.
Earlier, scientists discovered miles-long, wind-scoured ridges called "yardangs" with the first Mars orbiter, Mariner 9, in the early 1970s.
New HiRISE images reveal surface texture and fine-scale features that are giving scientists insight on how yardangs form.
"HiRISE is showing us just how interesting layers in yardangs are," said Bridges. "HiRISE shows that some layers in the yardangs are made of softer materials that have been modified by wind," he added.
According to Bridges, the soft material could be volcanic ash deposits, or the dried up remnants of what once were mixtures of ice and dust, or something else.
"HiRISE keeps showing interesting things about terrains that I expected to be uninteresting," said HiRISE principal investigator Alfred McEwen of the UA's Lunar and Planetary Laboratory.
Researchers can now use HiRISE images to infer wind directions over the entire planet.