HiRise Scientists Are Challenged by Martian Winds
According to NASA, scientists working on the University on Arizona’s High Resolution Imaging Experiment, or HiRise, are being challenged to spell out the complex, wind-sculpted landforms they are seeing in unprecedented detail. This is an exciting concept since Mars has a tenuous atmosphere at less than 1% the surface pressure of Earth.
The most powerful camera to orbit another planet, the HiRise camera on NASA’s Mars Reconnaissance Orbiter can see 20-inch-diameter features while flying at about 7,500 miles per hour–about 155 and 196 miles above the Martian surface. HiRise is offering eye-opening new views of wind-driven Martian geology to researchers. But are winds on present-day Mars strong enough to form and change geological features? Or were wind-constructed formations made in the past when wind speeds and atmospheric pressures were higher.
HiRise team members are asking many questions: “We’re seeing what looks like smaller sand bedforms on the top of larger dunes, and, when we zoom in more, a third set of bedforms topping these.” HiRise co-investigator Nathan Bridges of the Jet Propulsion Laboratory in Pasadena, Calif. said, “On Earth, small bedforms can
form and change on time scales as short as a day.”
NASA science data is showing that there are two kinds of “bedforms”, or wind-deposited landforms. There are sand dunes which are typically larger and have distinct shapes, and sand mixed with coarser milli-metered-sized particles that are called ripples. They are typically smaller, more linear structures. According to Bridges, HiRise shows detail in sediments deposited by winds on the lee side of rocks. These rock “windtails” show which way the most current winds have blown.
An orbiting camera has never been used before to see these features. Only rovers and landers were used previously. Researchers to infer wind directions over the entire planet can now use HiRise images. In the early 1970’s, scientists, using the first Mars orbiter, Mariner 9 discovered miles-long, wind-scourged ridges called “yardangs”. Insight on how they form is being revealed by new HiRise images that show surface texture and fine-scale features. “Possibly the bedforms on the volcanoes formed under a different Martian climate in the past, when atmospheric density was greater,” Bridges said. “But I’m not sure that’s the case, because you can see evidence that a lot of the mantle appears to be fairly recent.”
He added that images showing what covers the slopes of the high Martian volcanoes are dunes or ripples that appear to have an organized “reticulate” structure–possibly formed by winds blowing from multiple directions. Also discovered were dark streaks coming from Victoria Crater, probably streaks of dark sand blown-out from the crater onto the surface. The wind might have blown away lighter-colored surface material, exposing a darker underlying surface.
This entry was posted on Saturday, February 2nd, 2008 at 9:25 pm and is filed under Space Agency News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
