Neon and oxygen can pass right through the boundary, and after a 30 year journey across out solar system, IBEX finds and measures them.
"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," Eric Christian, mission scientist for IBEX at NASA's Goddard Space Flight Center in Greenbelt, Md, said in a statement.
"IBEX's observations shed a whole new light on the mysterious zone where the solar system ends and interstellar space begins."
Scientists have published their findings in a series of papers in the Astrophysics Journal, and they've found the mix of particles in the interstellar wind are measurably different from what comes from our sun.
"Our solar system is different than the space right outside it and that suggests two possibilities," David McComas the principal investigator for IBEX at the Southwest Research Institute in San Antonio, Texas said. Either the solar system evolved in a separate, more oxygen-rich part of the galaxy than where we currently reside or a great deal of critical, life-giving oxygen lies trapped in interstellar dust grains or ices, unable to move freely throughout space."
Either way, this affects scientific models of how our solar system - and life - formed.