Scientists Discover Mars Atmosphere Altered By Solar Flares
Shown here is an example of the flare of 26 April 2001 and its effects at Earth and Mars. The X-rays recorded by the GOES spacecraft show a unambiguous flare with peak flux at 13:10 UT. At essentially the same time, an ionosphere observing station in Sondrestrom (Greenland), selected because it had a high latitude location comparable to the one for NASA's Mars Global Surveyor (MGS), recorded a dramatic increase in the electron density of the terrestrial ionosphere. At Mars, the MGS observations just six minutes later showed large increases in the lower portions of the martian ionosphere. This is the first time that the same solar flare was seen to cause modifications to the upper atmospheres of two planets [credit: This figure was provided by the Center for Space Physics at Boston University.]
by Staff Writers
Boston MA (SPX) Feb 23, 2006
Astronomers said Thursday they have uncovered the first clear evidence that solar flares can affect the upper atmosphere of Mars. A team at Boston University said their studies of X-ray bursts from the Sun in April 2001 that reached Mars show the phenomena caused dramatic enhancements to the planet's ionosphere - the region where the Sun's ultraviolet and X-rays are absorbed by atoms and molecules in the atmosphere.
Reporting in the Feb. 24 issue of the journal Science, the team said the Mars Global Surveyor spacecraft registered the flare's effects as it transmitted signals back to NASA's antenna sites 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," said lead researcher Michael Mendillo, of B.U.'s Center for Space Physics.
"At Earth, the GOES (geostationary weather) satellites measure the Sun's X-rays almost continuously," said co-research Paul Withers. "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 normally by the Sun's X-rays can cause subtle changes in MGS radio signals as they travel to Earth, so the team began to seek 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 David Hinson at Stanford University, who provides open access to researchers worldwide via a Web site.
"We needed Hinson's expert advice to make sure that some odd changes in the MGS radio signal had not occurred just by chance," Withers added.
To confirm that photons from solar flares produce sufficient magnetic fluxes to modify the Martian ionosphere, the team sought additional evidence using earthbound measurements. "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 said.
Using several ionospheric radars spread over the globe - operated by scientists at the University of Massachusetts at Lowell - team member Bodo Reinisch confirmed that the Sun's X-rays caused equally impressive modifications to Earth's ionosphere at the precise times required.
"The science yield from this work will be in the new field of comparative atmospheres," Mendillo said. "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, 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."
Topic: Solar flares thicken Mars' ionoshere! (Read 1080 times)