На информационном ресурсе применяются рекомендательные технологии (информационные технологии предоставления информации на основе сбора, систематизации и анализа сведений, относящихся к предпочтениям пользователей сети "Интернет", находящихся на территории Российской Федерации)

Science World

74 подписчика

Comet Siding Spring Triggered Meteor Storm on Mars, Say Scientists

Comet Siding Spring traveled from the most distant region of our Solar System, the Oort Cloud. It made a close approach to Mars on October 19, 2014, within about 139,500 km of the planet.

Dust from the comet impacted Mars and was vaporized high in the 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.

Data from observations carried out by two NASA and one ESA spacecraft have revealed that debris from the comet added a temporary and very strong layer of ions to the Mars’ ionosphere.

In these observations, the researchers were able to make a direct connection from the input of debris from a specific meteor shower to the formation of this kind of transient layer in response; that is a first on any planet, including Earth.

“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. 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 harm’s way,” said Dr Jim Green, director of NASA’s Planetary Science Division.

One of the NASA’s Mars orbiters, Mars Atmosphere and Volatile Evolution (MAVEN), detected the comet encounter in two ways.

The remote-sensing Imaging Ultraviolet Spectrograph observed intense UV emission 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’ UV spectrum for several hours after the encounter and then dissipated over the next two days.

“They call this comet encounter a once-in-a-lifetime event, but it’s more like once-in-a-million years. 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, so it must have been a spectacular event that night on Mars,” said Dr Nick Schneider of the University of Colorado Boulder.

“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 Prof Bruce Jakosky of the University of Colorado Boulder.

MAVEN also was able to directly sample and determine the composition of some of the comet dust in Mars’ atmosphere.

Analysis of these samples detected eight different types of metal ions, including sodium, magnesium and iron.

The Mars Advanced Radar for Subsurface and Ionospheric Soundinginstrument aboard ESA’s Mars Express spacecraft observed a huge increase in the density of electrons following the comet’s close approach.

This instrument saw a huge jump in the electron density in the ionosphere a few hours after the comet rendezvous.

This spike occurred at a substantially lower altitude than the normal density peak in the Martian ionosphere.

The Shallow Subsurface Radar aboard NASA’s Mars Reconnaissance Orbiter also detected the enhanced ionosphere.

Images from the instrument were smeared by the passage of the radar signals through the temporary ion layer created by the comet’s dust.

The scientists used this smearing to determine that the electron density of the ionosphere on the Mars’ night side, where the observations were made, was five to 10 times higher than usual.

Mars Reconnaissance Orbiter’s Compact Reconnaissance Imaging Spectrometer for Mars also observed the comet to see whether signs of any particular chemical constituents stood out in its spectrum.

“The spectrum appears to show a dusty comet with no strong emission lines at their instrument’s sensitivity,” the scientists said.

Source

Картина дня

наверх