Wednesday, August 20, 2014

Anio Valles

The sinuous channel at the bottom of today's VIS image is called Anio Valles.

Orbit Number: 55239 Latitude: 35.1204 Longitude: 57.3396 Instrument: VIS Captured: 2014-05-28 04:52

Photo credit: NASA/JPL-Caltech/Arizona State University

Colliding Atmospheres: Mars vs Comet Siding Spring

On October 19, 2014, Comet Siding Spring will pass by Mars only 132,000 km away--which would be like a comet passing about 1/3 of the distance between Earth and the Moon.

The nucleus of the comet won't hit Mars, but there could be a different kind of collision.

"We hope to witness two atmospheres colliding," explains David Brain of the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP). "This is a once in a lifetime event!"

Everyone knows that planets have atmospheres. Lesser known is that comets do, too. The atmosphere of a comet, called its "coma," is made of gas and dust that spew out of the sun-warmed nucleus. The atmosphere of a typical comet is wider than Jupiter.

"It is possible," says Brain, "that the atmosphere of the comet will interact with the atmosphere of Mars. This could lead to some remarkable effects — including Martian auroras."

The timing could scarcely be better. Just last year, NASA launched a spacecraft named MAVEN to study the upper atmosphere of Mars, and it will be arriving in September 2014 barely a month before the comet.

MAVEN is on a mission to solve a longstanding mystery: What happened to the atmosphere of Mars? Billions of years ago, Mars had a substantial atmosphere that blanketed the planet, keeping Mars warm and sustaining liquid water on its surface. Today, only a wispy shroud of CO2 remains, and the planet below is colder and dryer than any desert on Earth. Theories for this planetary catastrophe center on erosion of the atmosphere by solar wind.

"The goal of the MAVEN mission is to understand how external stimuli affect the atmosphere of Mars," says Bruce Jakosky of LASP, MAVEN's principal investigator. "Of course, when we planned the mission, we were thinking about the sun and the solar wind. But Comet Siding Spring represents an opportunity to observe a natural experiment, in which a perturbation is applied and we can see the response."

Brain, who is a member of the MAVEN science team, thinks the comet could spark Martian auroras. Unlike Earth, which has a global magnetic field that shields our entire planet, Mars has a patchwork of "magnetic umbrellas" that sprout out of the surface in hundreds of places all around the planet. If Martian auroras occur, they would appear in the canopies of these magnetic umbrellas.

"That is one thing that we will be looking for with both MAVEN and Hubble Space Telescope," says Brain. "Any auroras we see will not only be neat, but also very useful as a diagnostic tool for how the comet and the Martian atmosphere have interacted."

The atmosphere of the comet includes not only streamers of gas, but also dust and other debris blowing off the nucleus at 56 kilometers per second relative to Mars. At that velocity, even particles as small as half a millimeter across could damage spacecraft. NASA's fleet of Mars orbiters including MAVEN, Mars Odyssey and Mars Reconnaissance Orbiter will maneuver to put the body of Mars between themselves and the comet’s debris during the dustiest part of the encounter.

"It's not yet clear whether any significant dust or gas will hit the Mars atmosphere," cautions Jakosky. "But if it does, it would have the greatest effects on the upper atmosphere."

Meteoroids disintegrating would deposit heat and temporarily alter the chemistry of upper air layers. The mixing of cometary and Martian gases could have further unpredictable effects. Although MAVEN, having just arrived at Mars, will still be in a commissioning phase, it will use its full suite of instruments to monitor the Martian atmosphere for changes.

"By observing both before and after, we hope to determine what effects the comet dust and gas have on Mars, if any," says Jakosky.

Whatever happens, MAVEN will have a ringside seat.

Video credit: NASA

Tuesday, August 19, 2014

Channels in Infrared

Near the bottom of this nighttime IR image are several channels. The dusty channel floors are darker (colder) than the rocky walls.

Orbit Number: 55224 Latitude: 4.19544 Longitude: 318.675 Instrument: IR Captured: 2014-05-26 22:27

Image credit: NASA/JPL-Caltech/Arizona State University

Note: I am somewhat confused as to the actual location of this image. On the one hand, the coordinates suggest that these channels should be within Xanthe Terra, between Shalbatana Vallis to the west and Da Vinci Crater to the southeast. However, my global map of Mars does not correspond with either these coordinates or the context map provided on the THEMIS webpage. So I'm not quite sure whether the coordinates or the context map is correct.

Endeavour Crater Panorama

This panorama combines several images from the navigation camera on NASA's Mars Exploration Rover Opportunity to show the rover's surroundings after surpassing 25 miles (40.23 kilometers) of total driving on Mars.

The component images were taken on July 29, 2014, during the 3,737th Martian day, or sol, of Opportunity's work on Mars, prior to that sol's drive. The rover's location was the point it reached with a drive of 157 feet (48 meters) on Sol 3735 (July 27, 2014), which brought Opportunity's total odometry to 25.01 miles (40.25 kilometers).

The site is on the western side of the west rim of Endeavour Crater. This full-circle vista is centered approximately to the east, with the crater rim extending northward in the left half and southward in the right half.

Image credit: NASA/JPL-Caltech

Monday, August 18, 2014

Bonanza King

This image from the Mast Camera (Mastcam) on NASA's Curiosity Mars rover shows a portion of the pale rock outcrop that includes the "Bonanza King" target chosen for evaluation as the mission's fourth rock-drilling site. Raised ridges on the flat rocks -- possible mineral veins -- are visible at upper and middle right. Tread marks from one of Curiosity's wheels are visible in the lower half of the image.

The left camera of the Mastcam pair acquired this image on August 12, 2014, during the 707th Martian day, or sol, of Curiosity's work on Mars. The width of the ground covered in the foreground is about 2.5 feet (about 75 centimeters). The image is in the Mastcam's raw color, as recorded by the camera under Martian lighting conditions.

The location is on a ramp rising from the northeastern end of "Hidden Valley," between Curiosity's August 2012 landing site in Gale Crater and destinations on Mount Sharp within the crater.

Image credit: NASA/JPL-Caltech

Note: For more information, see PIA18597: Looking Up the Ramp Holding 'Bonanza King' on Mars, PIA18599: Down Northeastern Ramp into 'Hidden Valley' on Mars, PIA18600: View Down 'Hidden Valley' Ramp at 'Bonanza King' on Mars, and Curiosity Mars Rover Prepares for Fourth Rock Drilling.

Sunday, August 17, 2014

Glacial Ridges and Channels in Eastern Hellas Planitia

Hellas Crater in the ancient highlands contains some of the clearest evidence on Mars for glacial processes. This image, on the eastern margin of the giant impact crater, shows a number of features consistent with glaciation.

There are roughly north-south running ridges and troughs which mark the deposition of sediment called moraine underneath or beside a glacier. There are also sinuous channels which may formed from meltwater underneath a glacier. A small (3.5 x 3.5 kilometer) cutout shows an example of the moraine and meltwater channel.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18647: Glaciation at the Eastern Hellas Margin.

Saturday, August 16, 2014

Planum Boreum Layering

This VIS image shows the layering of the north polar cap.

Orbit Number: 55224 Latitude: 82.3714 Longitude: 287.856 Instrument: VIS Captured: 2014-05-26 22:55

Photo credit: NASA/JPL-Caltech/Arizona State University

Chasma Boreale Scarps

Chasma Boreale is the 560-kilometer long valley that cuts through the Northern Polar layered deposits of Mars.

The section that it exposes show fine scaled layering and a major unconformity, where the azimuth of the beds changes markedly. This is is characteristic of the polar layered deposits. The formation of the unconformity suggests a time when the lower sediments were being eroded rather than deposited. The extracted image shows a roughly 4 x 4 kilometer area across the unconformity.

The polar layered deposits are weakly cemented rocks, and so lying over the scarps you can see lines of mass wasting where dust and sand size particles have slumped downhill. This image is part of a planned stereo pair, and was in the late summer in the Northern Hemisphere of Mars.

Comparing images like this to those taken in previous years and in different seasons allows a more accurate understanding of current surface processes on the Red Planet.

This is a stereo pair with ESP_036515_2650.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18646: The Side of Chasma Boreale.

Friday, August 15, 2014

Olympia Undae (Again)

Today's VIS image shows more of Olympia Undae, a large dune field located near the north polar cap.

Orbit Number: 55192 Latitude: 80.3803 Longitude: 136.098 Instrument: VIS Captured: 2014-05-24 07:42

Photo credit: NASA/JPL-Caltech/Arizona State University

Lava Cones and Flows in Southern Elysium Planitia

The north end of this long image shows a lava surface in southern Elysium Planitia. Small cones are common on the extensive young flood lavas in this region.

Here, the cones are larger than usual, perhaps approaching cinder cone sizes. What's really odd here is that the cones are associated with lighter areas with polygonal patterns. Such polygons are commonly visible on the denser portions of lava flows, while the rougher areas have more broken-up low-density crust.

But the shapes of these regions are unusual, and the association with cones suggest that the cones were source vents for local lava flows. Other interpretations are also possible.

Image credit: NASA/JPL/University of Arizona

Note: For more information, see PIA18645: Strange Cones and Flows.

Thursday, August 14, 2014

Olympia Undae

Today's VIS image shows part of the margin of Olympia Undae.

Orbit Number: 55190 Latitude: 78.4215 Longitude: 197.221 Instrument: VIS Captured: 2014-05-24 03:04

Photo credit: NASA/JPL-Caltech/Arizona State University

An Irregular, Upright Boulder in Ophir Planum

This image was targeted to cover part of a small “chaos” terrain, where there are lots of steep slopes.

A closeup shows a boulder or block casting a long shadow, at the end of a boulder trail down the slope, and we can see it moved from upper left to middle right. The trail has a odd repeating pattern, as if the boulder couldn't roll straight due to its shape.

The sun angle and shadow length indicate the boulder is about 6 meters high, whereas its width as seen from overhead is only about 3.5 meters, so indeed it has an irregular shape. Furthermore, it came to rest with its long axis pointed up.

This is a stereo pair with ESP_035700_1765.

Image credit: NASA/JPL/University of Arizona

Note: This boulder is located in Ophir Planum. For more information, see PIA18594: An Irregular, Upright Boulder on Mars and Tall Boulder Rolls Down Martian Hill, Lands Upright.

Wednesday, August 13, 2014

Dunes on the Edge of Planum Boreum

The dunes in this VIS image are located right at the edge of the polar cap.

Orbit Number: 55188 Latitude: 83.2929 Longitude: 118.562 Instrument: VIS Captured: 2014-05-23 23:53

Photo credit: NASA/JPL-Caltech/Arizona State University

Tuesday, August 12, 2014

Ascraeus Mons

The lava flows in today's VIS image are part of Ascraeus Mons.

Orbit Number: 55157 Latitude: 15.6 Longitude: 258.525 Instrument: VIS Captured: 2014-05-21 11:00

Photo credit: NASA/JPL-Caltech/Arizona State University

Saturday, August 9, 2014

Dunes Near Olympia Undae

The dunes in this VIS image are near the large dune field called Olympia Undae.

Orbit Number: 55154 Latitude: 78.8498 Longitude: 154.617 Instrument: VIS Captured: 2014-05-21 04:38

Photo credit: NASA/JPL-Caltech/Arizona State University