Friday, October 12, 2012

"Game Changing" Images From The Mars Rover Curiosity

I thought for sure that the national airwaves would be buzzing endlessly about the discovery of river-worn pebbles by the Mars rover Curiosity on September 27. The announcement was made to the usual temporary fanfare and faded away predictably in unceremonious fashion. I guess that is the price we pay to live in this info-charged, "what-have-you-done-for-me-lately" world. If our attention spans get any shorter there will be nothing in the solar system that amazes us.

Well not for this old rock-hound, who remains duly impressed a full two weeks after the announcement was publicized. This truly is the smoking gun for the former presence of running water on Mars. Previous studies have shown that minute amounts of water still reside near the Martian poles and perhaps beneath the Martian surface elsewhere. But this is verifiable and visible evidence that rivers once ran on Mars! (A River Ran On It).

In this posting, I include images released by NASA with their own captions beautifully describing each one (I modified the captions slightly to reduce redundancy). The full story as posted on the NASA web site can be read and accessed here. Wow! This is really impressive. Stay tuned to NASA and this blog for more fantastic discoveries from Mars.

Where Water Flowed Downslope

This image shows the topography, with shading added, around the area where the rover Curiosity landed on Aug. 5 PDT (Aug. 6 EDT). Higher elevations are colored in red, with cooler colors indicating transitions downslope to lower elevations. The black oval indicates the targeted landing area for the rover known as the "landing ellipse," and the cross shows where the rover actually landed.

An alluvial fan, or fan-shaped deposit where debris spreads out downslope, has been highlighted in lighter colors for better viewing. On Earth, alluvial fans often are formed by water flowing downslope. New observations from Curiosity of rounded pebbles embedded with rocky outcrops provide concrete evidence that water did flow in this region on Mars, creating the alluvial fan. Water carrying the pebbly material is thought to have streamed downslope extending the alluvial fan, at least occasionally, to where the rover now sits studying its ancient history.

Remnants of Ancient Streambed on Mars

NASA's Curiosity rover found evidence for an ancient, flowing stream on Mars at a few sites, including the rock outcrop pictured here, which the science team has named "Hottah" after Hottah Lake in Canada’s Northwest Territories. It may look like a broken sidewalk, but this geological feature on Mars is actually exposed bedrock made up of smaller fragments cemented together, or what geologists call a sedimentary conglomerate. Scientists theorize that the bedrock was disrupted in the past, giving it the titled angle, most likely via impacts from meteorites.

The key evidence for the ancient stream comes from the size and rounded shape of the gravel in and around the bedrock. Hottah has pieces of gravel embedded in it, called clasts, up to a couple inches (few centimeters) in size and located within a matrix of sand-sized material. Some of the clasts are round in shape, leading the science team to conclude they were transported by a vigorous flow of water. The grains are too large to have been moved by wind. This image mosaic was taken by Curiosity's 100-millimeter Mastcam telephoto lens on its 39th Martian day, or sol, of the mission (Sept. 14, 2012 PDT/Sept. 15 GMT).

Close-up view of Hottah

A close-up view of Hottah reveals more details in the outcrop. Broken surfaces of the outcrop have rounded, gravel clasts, such as the one circled in white, which is about 1.2 inches (3 centimeters) across. Erosion of the outcrop results in gravel clasts that protrude from the outcrop and ultimately fall onto the ground, creating the gravel pile at left.


Gaelyn said...

Seems like water could indicate some form of life.

Joe Dirt said...

It would be interesting to know how sediment transport by water on Mars compares to transport by the same amount/velocity on Earth. I'm guessing the water on Mars can do more work with less water due to the lesser gravity and atmospheric density but maybe the effects of lesser gravity would be negated because both the water and sediment are affected equally. I recall a figure from a paper dealing with saltation and eolian transport on Mars (Iverson et al., 1976) showing much higher wind speeds were required on Mars to move sediment of a given size than on Earth due to the lower atmospheric density. I'm curious how fluvial transport would differ.