A change in the orbit of NASA’s Mars Odyssey spacecraft will give the Thermal Emission Imaging System (THEMIS) camera new views of Mars at a different local time of day: around sunrise and sunset. The spacecraft has been drifting toward the new orbit for more than a year, and a small engine burn on February 11, 2014 accelerated the drift; Odyssey will reach its new orbit in November 2015.
During the transition, THEMIS will continue observations as the orbital time of day changes from its current afternoon and pre-dawn local times. The new orbit will provide scientists with systematic views of Mars around local sunrise and sunset for the first time since the two Viking orbiters ceased operations more than a generation ago.
“We don’t know exactly what we’ll find when we get to an orbit where we see Mars just after sunrise,” says Philip Christensen (Arizona State University), who designed the new observing plan. He is THEMIS’ principal investigator.
Besides revealing landscapes in sharp relief thanks to the low Sun angle, the new orbital time of day for THEMIS promises to let scientists explore frosts, ground fogs, early morning clouds and hazes, and other transient atmosphere-related features that usually vanish as the Martian day goes on.
In addition, THEMIS will measure ground temperatures at thousands of locations. These observations can yield insight about materials in the ground and about temperature-driven processes. These include warm-season flows of water or brine seen on some slopes, and geysers fed by spring thawing of carbon dioxide ice near Mars’ south pole.
“Mars is a dynamic world,” says Christensen, “And for a generation we’ve not been positioned to explore this part of it so thoroughly.”