Science Seminars

Martian Mesospheric Clouds Observed by MAVEN/IUVS: Thermal Tides Coupled to the Upper Atmosphere

Speaker: Michael H. Stevens (Naval Research Laboratory)
Date: Thursday, Aug 17, 2017
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

The Imaging Ultraviolet Spectrograph (IUVS) on NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission has observed the Martian upper atmosphere since its arrival at Mars in late 2014. Although designed to measure the Martian dayglow between 90-200 km, IUVS also scans the limb down to 60 km where solar scattered light dominates the mid-ultraviolet (MUV) signal. Occasionally, this MUV signal reveals layers of enhanced scattered light between 60-80 km indicating the presence of detached mesospheric clouds. The Martian mesospheric cloud season typically extends for about one Earth year (about half a Martian year) centered around Martian aphelion. Over 100 scans containing mesospheric clouds are identified from October to December 2015, near the middle of the mesospheric cloud season. The clouds are preferentially distributed to the equator, consistent with previous observations. Their longitudinal distribution shows a strong wave three component suggesting forcing from a non-migrating tide, possibly linked to the Martian surface topography. Concurrent IUVS measurements from the upper atmosphere show that the wave 3 component enabling cloud formation is preserved 100 km above the clouds, providing strong evidence for coupling throughout this region. Preliminary observations from the current (2017) cloud season complementing the 2015 results will also be shown.