Status Report

Mars Odyssey THEMIS Image: Hadriaca Patera

By SpaceRef Editor

May 17, 2002

Filed under Daily Themis Pictures, Mars Odyssey THEMIS, US

Image Context:

Context image credit: NASA/Mars Orbiter Laser Altimeter (MOLA) Team

The Science

The Story

Although the largest volcanoes on Mars (and the solar system) are
located in the geologically young Tharsis region, there are many other
martian volcanoes that display equally interesting features, such as
Hadriaca Patera, shown in this image. Hadriaca Patera is located to the
northeast of the Hellas Planitia impact basin in the southern hemisphere.
Unlike the Tharsis volcanoes, Hadriaca Patera has very low relief, standing
only about 1-2 km above the surrounding plains. Many scientists believe
that Hadriaca Patera and other patera volcanoes (e.g., Tyrrhena) had
significant interaction with subsurface water that produced mostly
explosive ash deposits (pyroclastic flows), rather than just lava flows.
Nearby sources of water might have included Dao Vallis on the southern
flank of the volcano. The upper portion of this image shows relatively
smooth terrain located in the central caldera, which has been nearly filled
in with late-stage lava flows. The lower half of the image shows lobate
flows as well as furrows in the ash deposits that make up the volcano’s
southern flank; these erosional furrows may have formed by surface runoff
or sapping by groundwater. Just below the center of the image, a few small
sinuous troughs are visible, and may be collapsed lava tubes or collapse
features related to subsurface water. The number of impact craters on a
planetary surface is commonly used as a proxy for the age of the surface —
an old surface has had time to accumulate more craters than a young
surface. The relatively small number of large craters in the image
indicates that the surface in this area is younger than the nearby heavily
cratered ancient terrains outside the Hellas basin, but there are more
craters on this surface than would be found on the average volcanic surface
in Tharsis (there are some very large old craters on the volcano’s flank to
the southeast of this image). Paterae in general are older than the
Tharsis volcanoes. At the far right edge of the central portion of the
image, an ovoid-shaped crater is visible. Such craters are believed to
form by extremely low-angle impact events.

[Source: ASU THEMIS Science Team]

If you look at the context image to the right, you’ll see a large round circle. That’s the ancient mouth of the volcano, not a crater. This volcano is named Hadriaca Patera. Even though Mars is known as the home of the largest volcanoes in the solar system, this mile-high volcano isn’t very tall compared to its cousins in a region of Mars called Tharsis.

As a result, you might think that paterae volcanoes like this one are relatively undistinguished as Martian volcanoes go, but it turns out they are probably much older. The number of craters on the surface in the area tells us so. Older surfaces have had time to accumulate many more craters. Not all craters, however, are almost perfectly round. Look for the egg-shaped crater (far right edge of the central portion of the image). Crater shapes like this one are caused when an impacting body comes in toward the surface at an extremely low angle.

More than being older, paterae volcanoes are really interesting to scientists because they may have interacted with subsurface water. With that “ingredient,” these volcanoes spat out explosive ash deposits instead of just lava flows. Mars may look calm now, but wow! It sure wasn’t in the past.

There are many signs of the volcano’s past activity. In the upper portion of the image, the mouth of the volcano has been filled in with late-stage lava flows. Down below, a layering of flows is further scored with erosional furrows formed either by surface runoff or when groundwater eroded the surface from underneath, causing it to sink. Near the center of the image, collapsed lava tubes (or other collapse features related to subsurface water) texture the surface as well.

[Questions? Email marsoutreach@jpl.nasa.gov]

[Source: NASA/JPL Mars Outreach]

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA’s Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA’s Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

Image Credit: NASA/JPL/Arizona State University