“The Sun’s Astrosphere” –Did Moving Outside the Interstellar Boundary Cause Earth’s Mass Extinctions?



“The matter in our solar system contain much more oxygen than alien particles,” said Seth Redfield, a non-mission expert to help verify results from the space agency’s ongoing IBEX (Interstellar Boundary Explorer) mission, an unmanned probe that analyzes the interstellar boundary that protects much of our solar system, including the Earth, from deadly cosmic rays from interstellar space. “This surprised everyone. Now we have to find out why our matter is so oxygen rich.”

IBEX also offered researchers their first up-close look at particles of matter that came from outside our solar system. While theories previous to this analysis had long held that this matter would be substantially the same as the matter within our solar system, the data revealed a stark difference.

“We’ve detected alien matter that came into our solar system from other parts of the galaxy–and, chemically speaking, it’s not exactly like what we find here at home.” says David McComas the principal investigator for IBEX at the Southwest Research Institute in San Antonio, Texas.

"We've directly measured four separate types of atoms from interstellar space and the composition just doesn't match up with what we see in the solar system," says Eric Christian, mission scientist for IBEX at NASA's Goddard Space Flight Center Among the four types of atoms detected—H, He, O and Ne—the last one, neon, serves as a particularly useful reference. “Neon is a noble gas, so it doesn’t react with anything. And it’s relatively abundant, so we can measure it with good statistics,” explains McComas.

Using data from IBEX, the researchers team compared the neon-to-oxygen ratio inside vs. outside the heliosphere. In a series of six science papers appearing in the Astrophysical Journal, they reported that for every 20 neon atoms in the galactic wind, there are 74 oxygen atoms. In our own solar system, however, for every 20 neon atoms there are 111 oxygen atoms, which means that there is more oxygen in any given slice of the solar system than in local interstellar space.

“The interstellar boundary within the heliosphere, the part of space dominated by the sun, acts like a shield,” Redfield says. “It keeps the earth and much of the rest of the solar system protected from highly radio-active particles from us.”

The heliosphere, according to Redfield, is essentially the balance of the outward moving solar wind, which can travel upwards of a million miles per hour, and the compression of the gas and dust within it. It changes with time and our position with regards to the heliosphere and the interstellar boundary is important.

Stellar astrospheres–the plasma cocoons carved out of the interstellar medium by stellar winds–are one of several buffers that partially screen planetary atmospheres and surfaces from high-energy radiation. Screening by astrospheres is continually influenced by the passage of stars through the fluctuating density field of the interstellar medium (ISM). 

“If our planet slips out of the boundary our protection from galactic cosmic rays becomes much more tenuous,” said Redfield. “Then all we have to rely on is our atmosphere, which is likely not enough to keep much of this radiation from the planet.”

In fact, some have theorized that the earth moving outside of the interstellar boundary may have accounted for mass extinctions in the distant past, though Redfield is quick to point out that no hard evidence has yet been found.

IBEX data helped establish Earth’s relative location within the heliosphere and interstellar boundary, and provided information on Earth’s past and projected future paths through the boundary. IBEX also provided reference points that can be drawn upon as scientists begin to study similar structures around other stars.

“We are strongly convinced that most if not all stars have a structure similar to our heliosphere, which are called astrospheres,” Redfield says. The more we know about our heliosphere, the more we can learn about astrospheres as we look to other stars and solar systems for, among other things, possible conditions for life.”

The Daily Galaxy via nasa.gov/ibex and wesleyan.edu


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