Mars Spacecraft reveal comet flyby effects on Martian atmosphere

Two NASA and one European spacecraft, including NASA's MAVEN mission led by the University of Colorado Boulder, have gathered new information about the basic properties of a wayward comet that buzzed by Mars Oct. 19, directly detecting its effects on the Martian atmosphere.

Data from observations carried out by MAVEN, NASA's Mars Reconnaissance Orbiter (MRO) and the ESA's Mars Express spacecraft revealed that debris from the comet, known officially as Comet C/2013 A1 Siding Spring, caused an intense meteor shower and added a new layer of ions, or charged particles, to the ionosphere.

The ionosphere is an electrically charged region in the atmosphere that reaches from about 75 miles (120 kilometers) to several hundred miles above the Martian surface.

ESA's Mars Express spacecraft

Using the observations, scientists were able to make a direct connection between the input of debris from the meteor shower to the subsequent formation of the transient layer of ions, the first time such an event has been observed on any planet, including Earth, said the MAVEN research team.

The comet traveled from the most distant region of our solar system called the Oort Cloud and made a close approach at 2:27 p.m. EDT within about 87,000 miles (139,500 kilometers) of the Red Planet.

That is less than half the distance between Earth and our moon and less than one-tenth the distance of any known comet flyby of Earth.

"MAVEN is well suited for studying the effects of the dust from the comet in the Martian atmosphere, because it makes measurements at the altitudes where the dust was expected to have an effect," said CU-Boulder Professor Bruce Jakosky of the Laboratory for Atmospheric and Space Physics, the principal investigator on the $671 million Mars Atmosphere and Volatile EvolutioN (MAVEN) mission.

"We also should be able to see if there are long-term effects from the comet dust in that same region of the atmosphere."

The places where the red line on this graph extends higher than the blue line show detection of metals added to the Martian atmosphere from dust particles released by a passing comet. 

The graphed data are from the Imaging Ultraviolet Spectrograph (IUVS) on NASA's MAVEN spacecraft, which recorded the intensities of emission by ingredients in the Martian atmosphere just before (blue line) and after (red line) comet C/2013 A1 Siding Spring sped within about 87,000 miles (139,500 kilometers) of Mars on Oct. 19, 2014. 

The "before" line records the usual main gases in the atmosphere, primarily carbon dioxide and its byproducts.

The "after" line includes those plus peaks at 280 nanometer wavelength, a fingerprint of ionized magnesium, and other wavelengths that are fingerprints of iron.

Researchers interpret this change as a result of vaporisation of dust particles that came from the comet and entered the Martian atmosphere at high speed.

Imaging Ultraviolet Spectrograph (IUVS)

IUVS uses limb scans to map the chemical makeup and vertical structure across Mars' upper atmosphere.

Dust from the comet was vaporized high in the Martian atmosphere, producing what was likely an impressive meteor shower.

The debris resulted in significant but temporary changes to the planet's upper atmosphere and possible longer-term changes.

A host of Earth-based and orbiting telescopes also observed the unique celestial event.

The MAVEN spacecraft, recently arrived at Mars, detected the comet encounter in two ways.

The remote-sensing Imaging Ultraviolet Spectrograph (IUVS) designed and built at CU-Boulder observed intense ultraviolet emissions from magnesium and iron ions high in the atmosphere in the aftermath of the meteor shower.

Not even the most intense meteor storms on Earth have produced as strong a response as this one:

The emission dominated Mars' ultraviolet spectrum for several hours after the encounter and then dissipated over the next two days, according to the MAVEN science team.

MAVEN also was able to directly sample and help scientists determine the composition of some of the vaporised comet dust in Mars' atmosphere.

Analysis of these samples by the spacecraft's Neutral Gas and Ion Mass Spectrometer (NGIMS) designed and developed at NASA Goddard Space Flight Center in Greenbelt, Maryland, detected eight different types of metal ions, including sodium, magnesium and iron.

These are the first direct measurements of the composition of dust from an Oort Cloud comet.

The Oort Cloud, well beyond the outermost planets that surround our sun, is a spherical region of icy objects believed to be material left over from the formation of the solar system.

An illustration of Maven spacecraft at Mars. Credit: NASA

"They call this comet encounter a once-in-a-lifetime event, but it's more like once-in-a-million years," said CU-Boulder Associate Professor Nick Schneider, a LASP research associate and lead IUVS scientist for the mission.

"MAVEN got there just in time, and we were ready.

The numbers suggest a Martian would have seen many thousands of shooting stars per hour, possibly enough to be called a meteor storm, so it must have been a spectacular event that night on Mars."

Elsewhere above Mars, a joint U.S. and Italian instrument on Mars Express observed a huge increase in the density of electrons in the Martian ionosphere following the comet's close approach.

"This historic event allowed us to observe the details of this fast moving Oort Cloud comet in a way never before possible using our existing Mars missions," said Jim Green, director of NASA's Planetary Science Division at the agency's headquarters in Washington.

"Observing the effects on Mars of the comet's dust slamming into the upper atmosphere makes me very happy that we decided to put our spacecraft on the other side of Mars at the peak of the dust tail passage and out of harms way."

There are three CU-Boulder undergraduates and two graduate students on the IUVS science team, said Schneider, and there will be a number of additional CU-Boulder students working on MAVEN in the coming years.

Currently there are more than 100 students working on research projects at LASP, which provides hands-on training for future careers as engineers and scientists.

NASA MAVEN: Studying the passing of comet C/2013 A1 Siding Spring and its effects

This image shows an artist concept of NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission. 

Image Credit: NASA/GSFC

NASA's newest orbiter at Mars, MAVEN, took precautions to avoid harm from a dust-spewing comet that flew near Mars today and is studying the flyby's effects on the Red Planet's atmosphere.

The MAVEN spacecraft reported back to Earth in good health after about three hours of precautions against a possible collision with high-velocity dust particles released by comet C/2013 A1 Siding Spring.

"We're glad the spacecraft came through, we're excited to complete our observations of how the comet affects Mars, and we're eager to get to our primary science phase," said MAVEN Principal Investigator Bruce Jakosky of the University of Colorado, Boulder.

MAVEN began orbiting Mars on Sept. 21. The opportunity to study this rare near-miss of a planet by a comet comes during the project's commissioning phase.

A few weeks of instrument calibration and orbit fine-tuning remain before the start of the primary science phase. The mission will study the upper atmosphere of Mars and its interaction with the solar wind.

Comet Siding Spring hurtled past Mars today at about 125,000 mph (56 kilometers per second), coming within about 87,000 miles (139,500 kilometers) of the planet.

That is equivalent to about one-third of the distance between Earth and Earth's moon. The closest approach by the comet's nucleus came at about 11:27 a.m. PDT (2:27 p.m. EDT).

The period when dust from the comet was most likely to reach Mars and the orbits of spacecraft around Mars peaked about 100 minutes later.

From about 10:45 a.m. to 2 p.m. PDT (1:45 p.m. to 5:00 p.m. EDT) MAVEN kept in a defensive posture to reduce its profile relative to the direction from which the comet's high-velocity dust particles would come.

In that "hunkered down" orientation, its main antenna was not facing the right way for transmitting to Earth, so communications were maintained at low data rate via a secondary antenna.

Also, the mission performed a maneuver on Oct. 2 that set its orbit timing so that the spacecraft was behind Mars, relative to the possible dust flow, from about 12:53 p.m. to 1:23 p.m. PDT (3:53 p.m. to 4:23 p.m. EDT).

Downlink of data has begun from MAVEN observations of the comet and Mars' atmosphere. Some observations are designed to provide information about the composition of the gases and dust being released by the comet.

Others are investigating possible interaction between material from the comet and the atmosphere of Mars.

Three NASA Mars orbiters (MAVEN, Mars Reconnaisance Orbiter and Odyssey Orbiter), two Mars rovers (Curiosity and Opportunity) and other assets on Earth and in space are studying comet Siding Spring.

This comet is making its first visit this close to the sun from the outer solar system's Oort Cloud, so the concerted campaign of observations may yield fresh clues to our solar system's earliest days more than 4 billion years ago.

MAVEN's principal investigator is based at the University of Colorado's Laboratory for Atmospheric and Space Physics.

The university provided two science instruments and leads science operations, as well as education and public outreach, for the mission.