NASA’s Mars Spacecraft Maneuvers to Prepare for Close Comet Flyby

This graphic depicts the orbit of comet C/2013 A1 Siding Spring as it swings around the sun in 2014. 

On Oct. 19, the comet will have a very close pass at Mars. 

Its nucleus will miss Mars by about 82,000 miles (132,000 kilometers).

Image Credit: NASA/JPL-Caltech

NASA is taking steps to protect its Mars orbiters, while preserving opportunities to gather valuable scientific data, as Comet C/2013 A1 Siding Spring heads toward a close flyby of Mars on Oct. 19.

The comet’s nucleus will miss Mars by about 82,000 miles (132,000 kilometers), shedding material hurtling at about 35 miles (56 kilometers) per second, relative to Mars and Mars-orbiting spacecraft.

At that velocity, even the smallest particle, estimated to be about one-fiftieth of an inch (half a millimeter) across, could cause significant damage to a spacecraft.

NASA currently operates two Mars orbiters, with a third on its way and expected to arrive in Martian orbit just a month before the comet flyby.

Teams operating the orbiters plan to have all spacecraft positioned on the opposite side of the Red Planet when the comet is most likely to pass by.

"Three expert teams have modeled this comet for NASA and provided forecasts for its flyby of Mars," explained Rich Zurek, chief scientist for the Mars Exploration Program at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

"The hazard is not an impact of the comet nucleus, but the trail of debris coming from it. Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated."

"Mars will be right at the edge of the debris cloud, so it might encounter some of the particles -- or it might not."

During the day's events, the smallest distance between Siding Spring's nucleus and Mars will be less than one-tenth the distance of any known previous Earthly comet flyby.

The period of greatest risk to orbiting spacecraft will start about 90 minutes later and last about 20 minutes, when Mars will come closest to the center of the widening dust trail from the nucleus.

NASA's Mars Reconnaissance Orbiter (MRO)

NASA's Mars Reconnaissance Orbiter (MRO) made one orbit-adjustment maneuver on July 2 as part of the process of repositioning the spacecraft for the Oct. 19 event. An additional maneuver is planned for Aug. 27.

NASA's Mars Odyssey orbiter

The team operating NASA's Mars Odyssey orbiter is planning a similar maneuver on Aug. 5 to put that spacecraft on track to be in the right place at the right time, as well.

NASA's Mars Atmosphere and Volatile Evolution (MAVEN)

NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft is on its way to the Red Planet and will enter orbit on Sept. 21.

The MAVEN team is planning to conduct a precautionary maneuver on Oct. 9, prior to the start of the mission's main science phase in early November.

In the days before and after the comet's flyby, NASA will study the comet by taking advantage of how close it comes to Mars.

Researchers plan to use several instruments on the Mars orbiters to study the nucleus, the coma surrounding the nucleus, and the tail of Comet C/2013 A1 Siding Spring, as well as the possible effects on the Martian atmosphere.

This particular comet has never before entered the inner solar system, so it will provide a fresh source of clues to our solar system's earliest days.

MAVEN will study gases coming off the comet's nucleus into its coma as it is warmed by the sun.

MAVEN also will look for effects the comet flyby may have on the planet’s upper atmosphere and observe the comet as it travels through the solar wind.

Odyssey will study thermal and spectral properties of the comet's coma and tail. MRO will monitor Mars’ atmosphere for possible temperature increases and cloud formation, as well as changes in electron density at high altitudes.

The MRO team also plans to study gases in the comet’s coma. Along with other MRO observations, the team anticipates this event will yield detailed views of the comet’s nucleus and potentially reveal its rotation rate and surface features.

NASA Mars MSL Curiosity rover

Mars' atmosphere, though much thinner than Earth's, is thick enough that NASA does not anticipate any hazard to the Opportunity and Curiosity rovers on the planet's surface, even if dust particles from the comet hit the atmosphere and form into meteors.

Rover cameras may be used to observe the comet before the flyby, and to monitor the atmosphere for meteors while the comet's dust trail is closest to the planet.

Observations from Earth-based and space telescopes provided data used for modeling to make predictions about Siding Spring's Mars flyby, which were in turn used for planning protective maneuvers.

The three modeling teams were headed by researchers at the University of Maryland in College Park, the Planetary Science Institute in Tucson, Arizona, and JPL.

NASA MRO HiRISE: Active Dune Field on Mars

Nili Patera is one of the most active dune fields on Mars. 

As such, it is continuously monitored with the HiRISE (High Resolution Imaging Science Experiment) camera, a science instrument aboard NASA's Mars Reconnaissance Orbiter, with a new image acquired about every six weeks.

Image Credit: NASA /JPL-Caltech /Univ. of Arizona

By monitoring the sand dune changes, we can determine how winds vary seasonally and year-to-year. This observation is one of the more recent Nili images, acquired on March 1, 2014.

Compared to an image acquired on Nov. 22, 2012, changes are obvious.


The ripples on the dunes have moved, as well some of the dune boundaries, such as the one at upper left. New landslides on the central dune's lee face are apparent.

Such changes, in just 16 months (and finer scale changes have been seen in just a couple of weeks), demonstrate the effectiveness of wind in modifying the Martian landscape.

HiRISE is one of six instruments on NASA's Mars Reconnaissance Orbiter. The University of Arizona, Tucson, operates the orbiter's HiRISE camera, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo.

NASA Mars Curiosity Rover: Rover Near Martian Butte

NASA's Curiosity Mars rover and tracks from its driving are visible in this view from orbit, acquired on April 11, 2014, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.

Image Credit: NASA/JPL-Caltech/Univ. of Arizona

Scientists using NASA's Curiosity Mars rover are eyeing a rock layer surrounding the base of a small butte, called "Mount Remarkable," as a target for investigating with tools on the rover's robotic arm.

The rover works near this butte in an image taken on April 11 by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.

A rover's-eye view of Mount Remarkable and surroundings as seen from Curiosity's position in that HiRISE image is available in a mosaic of images from Curiosity's Navigation Camera (Navcam).

The butte stands about 16 feet (5 meters) high. Curiosity's science team refers to the rock layer surrounding the base of Mount Remarkable as the "middle unit" because its location is intermediate between rocks that form buttes in the area and lower-lying rocks that show a pattern of striations.

Depending on what the mission scientists learn from a close-up look at the rock and identification of chemical elements in it, a site on this middle unit may become the third rock that Curiosity samples with its drill.

The rover carries laboratory instruments to analyze rock powder collected by the drill.

The mission's first two drilled samples, in an area called Yellowknife Bay near Curiosity's landing site, yielded evidence last year for an ancient lakebed environment with available energy and ingredients favorable for microbial life.

NASA's Curiosity Mars rover and its tracks are visible in this view combining information from three observations by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. 

The image appears three-dimensional when viewed through red-blue glasses.

Image Credit: NASA/JPL-Caltech/Univ. of Arizona

NASA MRO HiRise Video: Leitmotif

NASA MARS HiRise Image: dark and dusty avalanche

Fallen soil and dust stains an icy cliffside on Mars. 

Credit: NASA/JPL/University of Arizona

Mars may be geologically inactive but that doesn't mean there's nothing happening there—seasonal changes on the Red Planet can have some very dramatic effects on the landscape, as this recent image from the HiRISE camera shows!

When increasing light from the springtime Sun warms up the sides of sheer cliffs made from countless layers of water and carbon dioxide ice near Mars' north pole, some of that CO2 ice sublimes, sending cascades of loose soil and dust down to the terraced base below.

This uncovered material stains the frost-covered polar surface dark, outlining the paths of avalanches for HiRISE to easily spot from orbit. (See the original HiRISE image here.)

Circling Mars since March 2006, the HiRISE camera aboard NASA's Mars Reconnaissance Orbiter has even captured some of these polar landslides in action.

The rust-colored avalanche shown above has fallen hundreds of meters from the middle of a layered ice deposit, spreading nearly a kilometer across the frozen ridges at the base of the cliff. The view was acquired on Sept. 13, 2013.

Check out a video explaining this view and the processes that created it below, narrated by Phil Plait (aka the Bad Astronomer).

MARS MRO Image: North Pole Weather forecasts

In winter a layer of frozen carbon dioxide covers the Martian North Pole. 

Approximately 50 percent of this ice cap falls to the ground as snow. 

This image was taken by NASA's Mars Reconaissance Orbiter (MRO) in 2006. 

Credits: NASA

In the north of the red planet snowfalls occur with great regularity.

Expeditions of Mars rovers into this region could therefore be easily planned.

Snowstorms lashing down at the northern hemisphere of Mars during the icy cold winters may be predicted several weeks in advance, say researchers from the Tohoku University in Sendai (Japan) and the Max Planck Institute for Solar System Research (MPS) in Katlenburg-Lindau (Germany) in their newest publication.

For the first time, the scientists' calculations show a connection between these snowfalls and a special Martian weather phenomenon: fluctuations of pressure, temperature, wind speeds, and directions that in the northern hemisphere propagate in a wave-like manner and occur very regularly.

For missions to the red planet exploring this region with rovers, such weather forecasts would offer the possibility of choosing a route that avoids heavy snow storms.

The Martian polar regions are an icy cold world. Similar to those on Earth they are covered by cohesive ice caps. In winter, when the temperatures drop below -128 degrees Celcius, this layer of ice is mainly supplied by frozen carbon dioxide from the atmosphere.

The ice caps then cover a region reaching south to about 70 degrees northern latitude. Only in the comparably warm Martian summer the carbon dioxide sublimates revealing the planet's eternal ice: a considerably smaller cap of frozen water.

Dr. Paul Hartogh

"Mars' seasonal ice has two different origins", says Dr. Paul Hartogh from the MPS. "A part of the carbon dioxide from the atmosphere condensates directly on the surface – similar to the way a layer of frost forms on Earth in cold, clear weather. Another part freezes in the atmosphere", he adds.

The tiny ice crystals accumulate into clouds and fall to the ground as snow.

In the new study, the researchers were now for the first time able to establish a connection between the occurrence of such ice clouds and a wave-like weather phenomenon characterized by a periodic change of pressure, temperature, wind speed, and -direction.

"This weather phenomenon on Mars is unique", says Dr. Alexander Medvedev from the MPS. Indeed, these so-called planetary waves can also be found in Earth's meteorology.

However, not only are the oscillations in pressure and temperature in the lower atmosphere much weaker here. They also occur much less regularly and their wave characteristics are much less pronounced.

"In the Martian northern hemisphere between fall and spring these waves can be found with astonishing reliability", the physicist adds. They propagate eastward with a uniform period of five to six days. Close to the surface, waves with higher frequencies can also be observed.