February 24th 06, 06:31 PM
http://www.bu.edu/phpbin/news/releases/display.php?id=1066
For Release Upon Receipt - February 23, 2006
Contact: Kira Edler, 617-358-1240,
BOSTON UNIVERSITY SCIENTISTS DISCOVER MARS' ATMOSPHERE ALTERED BY
SOLAR FLARES
New research shows X-ray bursts from the Sun cause dramatic changes
to the planet's ionosphere
(Boston) - Boston University astronomers announced today the first
clear
evidence that solar flares change the upper atmosphere of Mars. In an
article published in the February 24th issue of the journal Science,
the
researchers describe how X-ray bursts from the Sun in April 2001
recorded by satellites near Earth reached Mars and caused dramatic
enhancements to the planet's ionosphere - the region of a planet's
atmosphere where the Sun's ultraviolet and X-rays are absorbed by atoms
and molecules. The measurements were made by the Mars Global Surveyor
(MGS) spacecraft at the Red Planet as it transmitted signals to NASA's
antenna sites back on Earth.
"On April 15th and 26th of 2001, radio signals from MGS showed that the
Martian ionosphere was unusually dense, and this was the clue that some
extra production of ions and electrons had occurred," explained Michael
Mendillo, professor of astronomy, who led the BU research team in its
Center for Space Physics.
"At Earth, the GOES satellites measure the Sun's X-rays almost
continuously," said Dr. Paul Withers of BU. "Our search of their large
database discovered several cases of flares occurring just minutes
before MGS detected enhancements in Mars' ionosphere."
The extra electrons produced by the Sun's X-rays cause subtle changes
in
how the MGS radio waves travel toward Earth. Therefore, the team wanted
to find several unambiguous case study events before announcing their
findings.
The Radio Science Experiment on MGS has made observations of Mars'
ionosphere since its arrival there in late 1999. Its radio
transmissions
are received by NASA and then cast into scientifically meaningful data
by Dr. David Hinson at Stanford University who provides open access to
researchers worldwide via a Web site. "We needed Dr. Hinson's expert
advice to make sure that some odd changes in the MGS radio signal had
not occurred just by chance," Dr. Withers added.
To confirm that the photons from these flares had sufficient fluxes to
actually modify an ionosphere, additional evidence was sought using
measurements on Earth. "During this period, the Sun, Earth and Mars
were
nearly in a straight line and thus the X-rays measured at Earth should
have caused enhancements here as well as at Mars," Mendillo added.
Using several ionospheric radars spread over the globe, operated by
scientists at the University of Massachusetts/Lowell, Professor Bodo
Reinisch confirmed that the Sun's X-rays caused equally impressive
modifications to Earth's ionosphere at the precise times required on
those days.
"The science yield from this work will be in the new field of
Comparative Atmospheres," Mendillo pointed out. "By that I mean studies
of the same process in nature, in this case making an ionosphere on two
planets simultaneously, offer insights and constraints to models not
always possible when studying that process on a single planet. The
fifth
member of our team, Professor Henry Rishbeth of the University of
Southampton in England, provides the expertise in theory and modeling
that will be the focus of our follow-up studies."
Founded in 1839, Boston University is an internationally recognized
institution of higher education and research. With more than 30,000
students, it is the fourth largest independent university in the United
States. BU contains 17 colleges and schools along with a number of
multi-disciplinary centers and institutes which are central to the
school's research and teaching mission.
- 30 -
For Release Upon Receipt - February 23, 2006
Contact: Kira Edler, 617-358-1240,
BOSTON UNIVERSITY SCIENTISTS DISCOVER MARS' ATMOSPHERE ALTERED BY
SOLAR FLARES
New research shows X-ray bursts from the Sun cause dramatic changes
to the planet's ionosphere
(Boston) - Boston University astronomers announced today the first
clear
evidence that solar flares change the upper atmosphere of Mars. In an
article published in the February 24th issue of the journal Science,
the
researchers describe how X-ray bursts from the Sun in April 2001
recorded by satellites near Earth reached Mars and caused dramatic
enhancements to the planet's ionosphere - the region of a planet's
atmosphere where the Sun's ultraviolet and X-rays are absorbed by atoms
and molecules. The measurements were made by the Mars Global Surveyor
(MGS) spacecraft at the Red Planet as it transmitted signals to NASA's
antenna sites back on Earth.
"On April 15th and 26th of 2001, radio signals from MGS showed that the
Martian ionosphere was unusually dense, and this was the clue that some
extra production of ions and electrons had occurred," explained Michael
Mendillo, professor of astronomy, who led the BU research team in its
Center for Space Physics.
"At Earth, the GOES satellites measure the Sun's X-rays almost
continuously," said Dr. Paul Withers of BU. "Our search of their large
database discovered several cases of flares occurring just minutes
before MGS detected enhancements in Mars' ionosphere."
The extra electrons produced by the Sun's X-rays cause subtle changes
in
how the MGS radio waves travel toward Earth. Therefore, the team wanted
to find several unambiguous case study events before announcing their
findings.
The Radio Science Experiment on MGS has made observations of Mars'
ionosphere since its arrival there in late 1999. Its radio
transmissions
are received by NASA and then cast into scientifically meaningful data
by Dr. David Hinson at Stanford University who provides open access to
researchers worldwide via a Web site. "We needed Dr. Hinson's expert
advice to make sure that some odd changes in the MGS radio signal had
not occurred just by chance," Dr. Withers added.
To confirm that the photons from these flares had sufficient fluxes to
actually modify an ionosphere, additional evidence was sought using
measurements on Earth. "During this period, the Sun, Earth and Mars
were
nearly in a straight line and thus the X-rays measured at Earth should
have caused enhancements here as well as at Mars," Mendillo added.
Using several ionospheric radars spread over the globe, operated by
scientists at the University of Massachusetts/Lowell, Professor Bodo
Reinisch confirmed that the Sun's X-rays caused equally impressive
modifications to Earth's ionosphere at the precise times required on
those days.
"The science yield from this work will be in the new field of
Comparative Atmospheres," Mendillo pointed out. "By that I mean studies
of the same process in nature, in this case making an ionosphere on two
planets simultaneously, offer insights and constraints to models not
always possible when studying that process on a single planet. The
fifth
member of our team, Professor Henry Rishbeth of the University of
Southampton in England, provides the expertise in theory and modeling
that will be the focus of our follow-up studies."
Founded in 1839, Boston University is an internationally recognized
institution of higher education and research. With more than 30,000
students, it is the fourth largest independent university in the United
States. BU contains 17 colleges and schools along with a number of
multi-disciplinary centers and institutes which are central to the
school's research and teaching mission.
- 30 -