Home / Node / Ken Edgett Colloquium Abstract (Feb 15, 2017)

Ken Edgett Colloquium Abstract (Feb 15, 2017)

A more vast and accessible Martian sedimentary rock record

What was Earth like when life arose on our planet? Sedimentary rocks provide records of ancient environments, but the ever-active Earth did not preserve its oldest sediments. However, our neighboring world, Mars, did. Of course, we do not know whether Mars had life, but the planet has an older and accessible sedimentary rock record that can tell us something about environments that could be analogous to those of early Earth. The evidence that Mars has sedimentary rocks was first published in December 2000. Over the next 16 years, many important, related discoveries ensued. Some occurrences, such as a fossil river delta in Eberswalde crater, were eroded in a way that their form mimics and tells us about their original environment. Since 2000, the Martian sedimentary rocks that got the most attention were ones in which the rocks are layered, light toned, and have very few superimposed impact craters. Images from the Curiosity rover and the Mars Reconnaissance Orbiter have shown that the story is not so simple. The view is changing, radically. Those light-toned, layered rocks were just a sub-set of a greater whole. Sedimentary rocks are prevalent throughout the planet’s ancient, heavily cratered terrain and include cases that have been mistaken for lavas, for decades, because of their tone, composition, and resistance to erosion. In addition, the manner in which sedimentary rocks erode is a major contributor to the expression of Martian landscapes.

Technical Talk:

Curiosity’s Mars Hand Lens Imager (MAHLI) in Gale crater

The Mars Hand Lens Imager (MAHLI) is a high-resolution color camera mounted on the Curiosity rover’s robotic arm. It can observe rocks and regolith at resolutions as high as 14-20 microns per pixel. MAHLI was designed to be robust to challenging environments (including dust, temperature, vibration) and work within a specific scientific and engineering trade-space that permits distinction of very fine sand from coarse silt; facilitates identification of rock, regolith, and eolian sediment properties as good as or better than a geologist’s hand lens; acquires images, mosaics, focus stacks, and stereo/multiple images for three-dimensional views; all while having a sufficient field of view and ability to focus at a range of distances so that the camera can do high resolution imaging, context imaging, sample extraction documentation, and hardware inspection. Since landing in 2012, MAHLI images have contributed to major science findings through direct observation of geologic targets and through science-enabling support imaging (e.g., wheel inspections; tool placement). MAHLI has been invaluable for distinguishing mudstones and sandstones; especially sandstones because identification of some of them has been quite challenging. Overall, the strata examined are fluvial conglomerates; fluvial, deltaic, and eolian sandstones; and very fine-grained rocks that include lacustrine mudstones. A copy of MAHLI, named WATSON (Wide Angle Topographic Sensor for Operations and eNgineering), will accompany the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument on NASA’s Mars 2020 rover.
Technical talk abstract (PDF)