Mars ASU THEMIS camera to get new views of Red Planet

ASU's Thermal Emission Imaging System (THEMIS) is taking regular temperature measurements of the ground as the orbit of NASA's Mars Odyssey spacecraft drifts toward a time of day that will give THEMIS views of Mars around sunrise and sunset. 

This will be the first systematic observations of these times of day in more than a generation. 

Here, THEMIS is imaging the floor of Gale Crater, using its visual wavebands to create a color view of the area where Mars rover Curiosity (too small to be imaged) is exploring for ancient habitable environments. 

Image courtesy NASA /JPL-Caltech /Arizona State University.

For the first time since the Viking Mars mission of the 1970s, which ended more than a generation ago, scientists will soon begin systematic observations of Mars from orbit at times of day around local sunrise and sunset.

The instrument they will use is the Thermal Emission Imaging System (THEMIS) camera, designed at Arizona State University.

Mars Odyssey carries three main science instruments: The Gamma Ray Spectrometer (GRS), the Thermal Emission Imaging System (THEMIS), and the Mars Radiation Environment Experiment (MARIE).

The spacecraft has been drifting toward the new orbit for more than a year, and a small engine burn on Feb. 11 accelerated the drift so it can finalize the orbit in November of 2015.

During the transition, THEMIS will continue observations as the orbital time of day changes.

Philip Christensen

"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, designer and principal investigator for THEMIS.

He is a Regents' Professor of Geological Sciences in ASU's School of Earth and Space Exploration on the Tempe campus. Christensen developed the post-orbit change observing plan.

THEMIS is a multi-band camera that images Mars in nine infrared (heat-sensitive) "colours" and five visible ones. It was launched on Mars Odyssey in April 2001 and reached the Red Planet in October that year.

The spacecraft spent several months dipping into the Martian atmosphere to regularize its orbit, and THEMIS began science imaging in February 2002.

With more than 12 years elapsed since arrival, Mars Odyssey is the longest-working Mars spacecraft of any nation.


Morning and evening on Mars
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.

"We know that in places, carbon dioxide frost forms overnight," says Christensen. "And then it sublimates immediately after sunrise."

"What would this process look like in action? How would it behave? We've never observed this kind of phenomenon directly."

He notes that the Martian atmosphere is more variable than scientists have appreciated in the past.

"We can look for seasonal differences," says Christensen. "Are fogs more common in winter or spring? Do they vary from day to day? From one part of the year to another? From year to year? We'll check it out."

In addition, THEMIS will measure surface 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 gas-and-sand geysers fed by spring thawing of carbon dioxide ice near Mars' south pole.

Jeffrey Plaut

"We're teaching an old spacecraft new tricks," says Odyssey project scientist Jeffrey Plaut at NASA's Jet Propulsion Laboratory in Pasadena, California.

"We will be in position to do something that has never been done systematically: to watch how morning fog, clouds and surface frost develop at different times of year."

After Mars Odyssey reaches its intended orbit of 6:45 a.m. and p.m. (local time) in November 2015, mission engineers expect Odyssey will have enough propellant for nine to 10 more years of operation, an important matter for ongoing Mars exploration.

Besides conducting its own observations, Odyssey also serves as a crucial communications relay to Earth for the two active rovers, Curiosity and Opportunity, operating on the Martian surface.

"Mars is a dynamic world," says Christensen. "And for a generation, we've not been positioned to explore this part of it so thoroughly."

Cassini gets new views of Titan's land of lakes

This false-colour mosaic, made from infrared data collected by NASA's Cassini spacecraft, reveals the differences in the composition of surface materials around hydrocarbon lakes at Titan, Saturn's largest moon. 

Credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

With the sun now shining down over the north pole of Saturn's moon Titan, a little luck with the weather, and trajectories that put the spacecraft into optimal viewing positions, NASA's Cassini spacecraft has obtained new pictures of the liquid methane and ethane seas and lakes that reside near Titan's north pole.

The images reveal new clues about how the lakes formed and about Titan's Earth-like "hydrologic" cycle, which involves hydrocarbons rather than water.

While there is one large lake and a few smaller ones near Titan's south pole, almost all of Titan's lakes appear near the moon's north pole.

Cassini scientists have been able to study much of the terrain with radar, which can penetrate beneath Titan's clouds and thick haze.

And until now, Cassini's visual and infrared mapping spectrometer and imaging science subsystem had only been able to capture distant, oblique or partial views of this area.

Several factors combined recently to give these instruments great observing opportunities. Two recent flybys provided better viewing geometry.

Sunlight has begun to pierce the winter darkness that shrouded Titan's north pole at Cassini's arrival in the Saturn system nine years ago.

A thick cap of haze that once hung over the north pole has also dissipated as northern summer approaches. And Titan's beautiful, nearly cloudless, rain-free weather continued during Cassini's flybys this past summer.

The images are mosaics in infrared light based on data obtained during flybys of Titan on July 10, July 26, and Sept. 12, 2013.

The colorised mosaic from the visual and infrared mapping spectrometer, which maps infrared colors onto the visible-color spectrum, reveals differences in the composition of material around the lakes.

The data suggest parts of Titan's lakes and seas may have evaporated and left behind the Titan equivalent of Earth's salt flats.

Only at Titan, the evaporated material is thought to be organic chemicals originally from Titan's haze particles that once dissolved in liquid methane.

They appear orange in this image against the greenish backdrop of Titan's typical bedrock of water ice.

Almost all of the hydrocarbon seas and lakes on the surface of Saturn's moon Titan cluster around the north pole, as can be seen in this mosaic from NASA's Cassini mission. 

This mosaic, made from near-infrared images of Titan obtained by Cassini's imaging science subsystem, shows a view from the north pole (upper middle of mosaic) down to near the equator at the bottom. 

Credit: NASA/JPL-Caltech/SSI/JHUAPL/Univ. of Arizona

"The view from Cassini's visual and infrared mapping spectrometer gives us a holistic view of an area that we'd only seen in bits and pieces before and at a lower resolution," said Jason Barnes, a participating scientist for the instrument at the University of Idaho, Moscow.

"It turns out that Titan's north pole is even more interesting than we thought, with a complex interplay of liquids in lakes and seas and deposits left from the evaporation of past lakes and seas."