Ralph Milliken

About

Ralph Milliken is a Professor in the Department of Earth, Environmental & Planetary Sciences at Brown University. His research focuses on exploring the geology of planetary surfaces and utilizing remote sensing methods, such as satellite and rover-based data, to address geologic problems. His specific interests include understanding the distribution and role of water in the evolution of the solar system, quantifying mineral and volatile abundances in geologic materials through reflectance spectroscopy, and investigating the sedimentary rock record of Mars. His group integrates experiments, theory, and field/spacecraft data to advance these research areas. Professor Milliken is a science team member for the Mars Curiosity rover and participates in projects mapping water on the Moon, conducting laboratory studies of meteorites, and performing field studies of potential Mars analogs. He has contributed to NASA-funded research, including analyzing samples from the asteroid Bennu as part of the OSIRIS-REx mission, and is involved in efforts to understand the origins of life on Earth through space-related sample analysis. Additionally, he engages in educational outreach, supporting students in environmental science and space-related projects.

Research topics

• Astrobiology
• Geochemistry
• Mineralogy
• Geology

Selected publications

• Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples

  Science · 2022 · 307 citations

  Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide-bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu's parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carb…

  DOI

• Asteroid (101955) Bennu in the laboratory: Properties of the sample collected by <scp>OSIRIS</scp>‐<scp>REx</scp>

  Meteoritics and Planetary Science · 2024-06-26 · 166 citations

  articleOpen access

  Abstract On September 24, 2023, NASA's OSIRIS‐REx mission dropped a capsule to Earth containing ~120 g of pristine carbonaceous regolith from Bennu. We describe the delivery and initial allocation of this asteroid sample and introduce its bulk physical, chemical, and mineralogical properties from early analyses. The regolith is very dark overall, with higher‐reflectance inclusions and particles interspersed. Particle sizes range from submicron dust to a stone ~3.5 cm long. Millimeter‐scale and l…

  PublisherOA PDFDOI

• Thermally altered subsurface material of asteroid (162173) Ryugu

  Nature Astronomy · 2021-01-04 · 82 citations

  articleOpen access
  PublisherOA PDFDOI

• Reassigning CI chondrite parent bodies based on reflectance spectroscopy of samples from carbonaceous asteroid Ryugu and meteorites

  Science Advances · 2023-12-06 · 24 citations

  articleOpen access

  The carbonaceous asteroid Ryugu has been explored by the Hayabusa2 spacecraft to elucidate the actual nature of hydrous asteroids. Laboratory analyses revealed that the samples from Ryugu are comparable to unheated CI carbonaceous chondrites; however, reflectance spectra of Ryugu samples and CIs do not coincide. Here, we demonstrate that Ryugu sample spectra are reproduced by heating Orgueil CI chondrite at 300°C under reducing conditions, which caused dehydration of terrestrial weathering produ…

  PublisherOA PDFDOI

• Space weathering acts strongly on the uppermost surface of Ryugu

  Communications Earth & Environment · 2023-09-27 · 23 citations

  articleOpen access

  Abstract Returned samples from Cb-type asteroid (162173) Ryugu exhibit very dark spectra in visible and near-infrared ranges, generally consistent with the Hayabusa2 observations. A critical difference is that a structural water absorption of hydrous silicates is around twice as deep in the returned samples compared with those of Ryugu’s surface, suggesting Ryugu surface is more dehydrated. Here we use laboratory experiments data to indicate the spectral differences between returned samples and…

  PublisherOA PDFDOI

Frequent coauthors

• B. L. Ehlmann

  California Institute of Technology

  192 shared

• John F. Mustard

  Brown University

  186 shared

• F. Poulet

  Université Paris-Saclay

  178 shared

• S. L. Murchie

  177 shared

• J. L. Bishop

  Search for Extraterrestrial Intelligence

  146 shared

• Gregg A. Swayze

  United States Geological Survey

  135 shared

• L. H. Roach

  88 shared

• J. J. Wray

  86 shared

Similar researchers at Brown University

• Yongsong Huangh-95
• Tim Herberth-66