UNIVERSITY PARK, Pa. — Three Penn State faculty — Kate Freeman, Evan Pugh University Professor of Geosciences, Christopher House, professor of geosciences, and Allison Baczynski, associate research professor of geosciences — have been selected to join the NASA Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission to analyze samples from the asteroid Bennu.
As part of the Participating Scientist Program, the team will receive just over $1,000,000 over three years to measure the abundances of stable isotopes in organic matter and organic molecules contained within the samples. Their work will help scientists learn about the formation of the solar system and about molecules that may have contributed to the development of life on Earth.
The OSIRIS-REx mission is the United States’ first to collect a sample from an asteroid and deliver it to Earth for study. The mission launched on Sept. 8, 2016. The spacecraft reached Bennu in 2018, collected a sample late in 2020, and is now bringing it back to Earth for an anticipated delivery of Sept. 24, 2023.
The mission’s objectives are to investigate how planets and asteroids formed, as well as to further understand the hazards such asteroids pose to Earth. Asteroids can act as time capsules, preserving the earliest history of our solar system and chemical signatures of the ancestral building blocks of life. Bennu is an ideal asteroid to sample, according to the researchers — It is rich in carbon, a key element necessary for life, and has not changed much in 4.5 billion years.
The research team will receive approximately two grams of asteroid material, roughly the size of a sugar packet. The team will measure the sample using four cutting-edge methods, all developed or refined by the investigators. These will take the team from individual grains of the sample to its molecular scale.
The team will focus on the evaluation of molecules present on Bennu, as well as their isotopic signatures. Isotopes are atoms of the same element that differ slightly in mass due to having different numbers of neutrons in their nucleus. Isotopes of an element all share the same chemistry, but vary widely among materials in space, and can help identify the origins of molecules. The team will investigate what these molecules and the isotopes they carry can say about Bennu’s origins and how these molecules have transformed over time.
To do this, the team will use a high-precision method developed by Baczynski and Freeman at Penn State to measure isotopes present in a whole molecule. Using even newer mass spectrometry methods, the team will measure the isotopes at specific locations within molecules, giving clues to how molecules were synthesized.
“Different isotope patterns carried by a carboxyl group, a ketone, an amino acid, or an amine group will allow us to see how parts of molecules were built from material derived from interstellar space versus within the solar system,” said Freeman.
The solar system formed from the solar nebula — a disk of gas and dust (mainly hydrogen) surrounding the early sun — which started at hot temperatures.
“You start to condense out from the gas, dusts and grains that ultimately build up to rocks and then into small bodies which are called planetesimals,” said House. “That generates what we call primitive material.”
In addition to characterizing isotopes of molecules, the team will analyze insoluble organic carbon, nitrogen and sulfur isotopes by burning, collecting and measuring the gases released using an instrument Baczynski and Freeman developed. The next step will take the team to the University of California, Los Angeles (UCLA) where they will use secondary ion mass spectrometry (SIMS) to blast a beam of ions at the sample to release carbon atoms for isotope analysis.
“Isotope and molecule studies were already planned as part of the OSIRIS-REx mission, but what Penn State brings to the project is the ability to do the analyses with much smaller quantities than is possible using commercial instruments,” said Freeman. “We’ve developed methods in our lab that take us down orders of magnitude, so we can measure much smaller amounts of sample, which is perfect when all you have is a sugar packet-size of sample.”
The research is supported by NASA.