Mercury, our smallest planetary neighbor, has very little to
call an atmosphere, but it does have a strange weather pattern: morning
micro-meteor showers.
Recent modeling along with previously published results from NASA’s MESSENGER spacecraft — short for Mercury Surface, Space Environment, Geochemistry and Ranging, a mission that observed Mercury from 2011 to 2015 — has shed new light on how certain types of comets influence the lopsided bombardment of Mercury’s surface by tiny dust particles called micrometeoroids. This study also gave new insight into how these micrometeoroid showers can shape Mercury’s very thin atmosphere, called an exosphere.
The research, led by Petr Pokorný, Menelaos Sarantos and Diego Janches of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, simulated the variations in meteoroid impacts, revealing surprising patterns in the time of day impacts occur. These findings were reported in The Astrophysical Journal Letters on June 19, 2017.
“Observations by MESSENGER indicated that dust must predominantly arrive at Mercury from specific directions, so we set out to prove this with models,” Pokorný said. This is the first such simulation of meteoroid impacts on Mercury. “We simulated meteoroids in the solar system, particularly those originating from comets, and let them evolve over time.”
Earlier findings based on data from MESSENGER’s Ultraviolet and Visible Spectrometer revealed the effect of meteoroid impacts on Mercury’s surface throughout the planet’s day. The presence of magnesium and calcium in the exosphere is higher at Mercury’s dawn — indicating that meteoroid impacts are more frequent on whatever part of the planet is experiencing dawn at a given time.
This dawn-dusk asymmetry is created by a combination of Mercury’s
long day, in comparison to its year, and the fact that many meteroids in
the solar system travel around the Sun in the direction opposite the
planets. Because Mercury rotates so slowly — once every 58 Earth days,
compared to a Mercury year, a complete trip around the Sun, lasting only
88 Earth days — the part of the planet at dawn spends a
disproportionately long time in the path of one of the solar system’s
primary populations of micrometeoroids. This population, called
retrograde meteoroids, orbits the Sun in the direction opposite the
planets and comprises pieces from disintegrated long-period comets.
These retrograde meteroids are traveling against the flow of planetary
traffic in our solar system, so their collisions with planets — Mercury,
in this case — hit much harder than if they were traveling in the same
direction.
These harder collisions helped the team further key in on the source of the micrometeoroids pummeling Mercury’s surface. Meteroids that originally came from asteroids wouldn’t be moving fast enough to create the observed impacts. Only meteoroids created from two certain types of comets — Jupiter-family and Halley-type — had the speed necessary to match the obseravations.
“The velocity of cometary meteoroids, like Halley-type, can exceed 224,000 miles per hour,” Pokorný said. “Meteoroids from asteroids only impact Mercury at a fraction of that speed.”
Jupiter-family comets, which are primarly influenced by our largest planet’s gravity, have a relatively short orbit of less than 20 years. These comets are thought to be small pieces of objects originating in the Kuiper Belt, where Pluto orbits. The other contributor, Halley-type comets, have a longer orbit lasting upwards of 200 years. They come from the Oort Cloud, the most distant objects of our solar system — more than a thousand times farther from the Sun than Earth.
The orbital distributions of both types of comets make them ideal candidates to produce the tiny meteoroids that influence Mercury’s exosphere.
Pokorný and his team hope that their initial findings will improve our understanding of the rate at which comet-based micrometeoroids impact Mercury, further improving the accuracy of models of Mercury and its exosphere.
Related:
Recent modeling along with previously published results from NASA’s MESSENGER spacecraft — short for Mercury Surface, Space Environment, Geochemistry and Ranging, a mission that observed Mercury from 2011 to 2015 — has shed new light on how certain types of comets influence the lopsided bombardment of Mercury’s surface by tiny dust particles called micrometeoroids. This study also gave new insight into how these micrometeoroid showers can shape Mercury’s very thin atmosphere, called an exosphere.
The research, led by Petr Pokorný, Menelaos Sarantos and Diego Janches of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, simulated the variations in meteoroid impacts, revealing surprising patterns in the time of day impacts occur. These findings were reported in The Astrophysical Journal Letters on June 19, 2017.
“Observations by MESSENGER indicated that dust must predominantly arrive at Mercury from specific directions, so we set out to prove this with models,” Pokorný said. This is the first such simulation of meteoroid impacts on Mercury. “We simulated meteoroids in the solar system, particularly those originating from comets, and let them evolve over time.”
Earlier findings based on data from MESSENGER’s Ultraviolet and Visible Spectrometer revealed the effect of meteoroid impacts on Mercury’s surface throughout the planet’s day. The presence of magnesium and calcium in the exosphere is higher at Mercury’s dawn — indicating that meteoroid impacts are more frequent on whatever part of the planet is experiencing dawn at a given time.
Scientists used models along with earlier findings
from the MESSENGER mission to shed light on how certain types of comets
influence the micrometeoroids that preferentially impact Mercury on the
dawn side of the planet. Here, data from the Mercury Atmosphere and
Surface Composition Spectrometer, or MASCS, instrument is overlain on
the mosaic from the Mercury Dual Imaging System, or MDIS.
Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
These harder collisions helped the team further key in on the source of the micrometeoroids pummeling Mercury’s surface. Meteroids that originally came from asteroids wouldn’t be moving fast enough to create the observed impacts. Only meteoroids created from two certain types of comets — Jupiter-family and Halley-type — had the speed necessary to match the obseravations.
“The velocity of cometary meteoroids, like Halley-type, can exceed 224,000 miles per hour,” Pokorný said. “Meteoroids from asteroids only impact Mercury at a fraction of that speed.”
Jupiter-family comets, which are primarly influenced by our largest planet’s gravity, have a relatively short orbit of less than 20 years. These comets are thought to be small pieces of objects originating in the Kuiper Belt, where Pluto orbits. The other contributor, Halley-type comets, have a longer orbit lasting upwards of 200 years. They come from the Oort Cloud, the most distant objects of our solar system — more than a thousand times farther from the Sun than Earth.
The orbital distributions of both types of comets make them ideal candidates to produce the tiny meteoroids that influence Mercury’s exosphere.
Pokorný and his team hope that their initial findings will improve our understanding of the rate at which comet-based micrometeoroids impact Mercury, further improving the accuracy of models of Mercury and its exosphere.
Related:
Last Updated: Sept. 29, 2017
Editor: Rob Garner
Eugene N. Parker, professor emeritus at the University of
Chicago, today visited the spacecraft that bears his name: NASA’s Parker
Solar Probe. This is the first NASA mission that has been named for a
living researcher, and is humanity’s first mission to the Sun.
Parker proposed the existence of the constant outflow of solar material from the sun, which is now called the solar wind, and theorized other fundamental stellar science processes. On Oct. 3, 2017, he viewed the spacecraft in a clean room at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, where the probe was designed and is being built. He discussed the revolutionary heat shield and instruments with the Parker Solar Probe team and learned how the spacecraft will answer some of the crucial questions Parker identified about how stars work.
NASA’s Parker Solar Probe is scheduled for launch on July 31, 2018, from Cape Canaveral Air Force Station, Florida. The spacecraft will explore the Sun’s outer atmosphere and make critical observations that will answer decades-old questions about the physics of stars. The resulting data will also improve forecasts of major eruptions on the sun and subsequent space weather events that impact life on Earth, as well as satellites and astronauts in space.
Parker proposed the existence of the constant outflow of solar material from the sun, which is now called the solar wind, and theorized other fundamental stellar science processes. On Oct. 3, 2017, he viewed the spacecraft in a clean room at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, where the probe was designed and is being built. He discussed the revolutionary heat shield and instruments with the Parker Solar Probe team and learned how the spacecraft will answer some of the crucial questions Parker identified about how stars work.
NASA’s Parker Solar Probe is scheduled for launch on July 31, 2018, from Cape Canaveral Air Force Station, Florida. The spacecraft will explore the Sun’s outer atmosphere and make critical observations that will answer decades-old questions about the physics of stars. The resulting data will also improve forecasts of major eruptions on the sun and subsequent space weather events that impact life on Earth, as well as satellites and astronauts in space.
Eugene Parker, professor emeritus at the University
of Chicago, visiting the spacecraft that bears his name, NASA’s Parker
Solar Probe, on Oct. 3, 2017. Engineers in the clean room at the Johns
Hopkins Applied Physics Laboratory in Laurel, Maryland, where the probe
was designed and is being built point out the instruments that will
collect data as the mission travels directly through the Sun’s
atmosphere.
Credits: NASA/JHUAPL
Eugene Parker (center), professor emeritus at the
University of Chicago, visits the spacecraft that bears his name: NASA’s
Parker Solar Probe. Thomas Zurbuchen (bottom right), the associate
administrator for NASA’s Science Mission Directorate, and Ralph Semmel
(behind Parker), the director for the Johns Hopkins Applied Physics
Laboratory in Laurel, Maryland, where the probe was designed and is
being built, joined the tour.
Credits: NASA/JHUAPL
Nicola Fox (bottom left), project scientist for
NASA’s Parker Solar Probe at the Johns Hopkins Applied Physics
Laboratory in Laurel, Maryland, describes the mission to the scientist
for whom it’s named: Eugene Parker (middle). Eugene Parker first
proposed the existence of the constant outflow of solar material from
the sun — now called the solar wind — through which the spacecraft will
travel. The red frame on the end of the spacecraft is a stand-in for the
mission’s thermal protection system, which will reach temperatures of
2,500 degrees F during its journey.
Credits: NASA/JHUAPL
Eugene Parker, professor emeritus at the University
of Chicago, visits the spacecraft that bears his name, NASA’s Parker
Solar Probe, at the Johns Hopkins Applied Physics Laboratory in Laurel,
Maryland, where the probe was designed and is being built. The
spacecraft is humanity’s first mission to a star — it will travel
directly through the Sun’s atmosphere.
Credits: NASA/JHUAPL
Last Updated: Oct. 3, 2017
Editor: Rob Garner
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