Some 40 thousand tons of extraterrestrial material fall on Earth every year. This cosmic debris provides cosmochemist Conel Alexander with information about the formation of the Solar System, our galaxy, and perhaps the origin of life.

Alexander studies meteorites to determine what went on before and during the formation of our Solar System. Meteorites are fragments of asteroids—small bodies that originated between Mars and Jupiter—and are likely the last remnants of objects that gave rise to the terrestrial planets. He is particularly interested in the analysis of chondrules, millimeter-size spherical objects that are the dominant constituent of the most primitive types of meteorites. Chondrules formed as molten droplets prior to the formation of the asteroids.

 Alexander develops techniques to measure precisely the different isotopes, atoms of the same element with different numbers of neutrons, of potassium, iron, magnesium, and oxygen in meteorite samples. Depending on the conditions, these elements may have evaporated and recondensed during chondrule formation. The isotopic compositions can indicate the extent of evaporation and recondensation, which can reveal the conditions under which the chondrules formed.

Alexander's other major interest is presolar materials preserved in meteorites. These include the tiny grains that emerged around dying stars and interstellar organic matter. By deciphering these relics, he hopes to understand the processes of galaxy evolution, the formation of the elements inside stars via nucleosynthesis, and stellar evolution.

In recent years, evidence has mounted that meteorites may have played a role in the origin of life on Earth. Alexander studies this possibility as part of his work on the origin of interstellar organic matter in meteorites. In addition, a small number of meteorites come from Mars. They have a wide age range and contain water-bearing minerals. By studying the hydrogen isotopes of this water, Alexander hopes to test ideas about what happened to the water that was originally on that planet.

Alexander received his B.S. Geology from  Imperial College, University of London and his Ph.D. in experimental physics from the University of Essex. For more information see

Explore Carnegie Science

Caltech logo
March 17, 2020

The Carnegie Institution for Science is consolidating our California research departments into an expanded presence in Pasadena. With this move, we are building on our existing relationship with Caltech, with a goal of broadening our historic collaborations in astronomy and astrophysics and pursuing new opportunities in ecology and plant biology that will support the global fight against climate change.

This plan, which affects our research operations in Pasadena and Palo Alto, reflects Carnegie’s ongoing efforts to extend our leadership in space, Earth, and life sciences and to enhance our ability to explore new frontiers.

In selecting our Pasadena location, we

 Illustration of DS Tuc AB by M. Weiss, CfA.
March 9, 2020

Pasadena, CA— A new kind of astronomical observation helped reveal the possible evolutionary history of a baby Neptune-like exoplanet.

To study a very young planet called DS Tuc Ab, a Harvard & Smithsonian Center for Astrophysics-led team that included six Carnegie astronomers—Johanna Teske, Sharon Wang, Stephen Shectman, Paul Butler, Jeff Crane, and Ian Thompson—developed a new observational modeling tool. Their work will be published in The Astrophysical Journal Letters and represents the first time the orbital tilt of a planet younger than 45 million years—or about 1/100th the age of the Solar System—has been measured.


John Mulchaey
March 2, 2020

Pasadena, CA—John Mulchaey, Director and Crawford H. Greenewalt Chair of the Carnegie Observatories, was presented with a Humanitarian STAR Award by the honor’s founding body—the Rotary Club of Sierra Madre. These recognitions, which reward “outstanding scientific and technological achievements with significant humanitarian benefit” were launched locally in 2015, but now include chapters and recipients from around the country.

Mulchaey was selected for the club’s Helios award in acknowledgment of his longstanding efforts at promoting outreach events and activities to share astronomy with enthusiasts of all ages throughout the Los Angeles area.

February 26, 2020

Washington, DC— Carnegie astronomers Stephen Shectman and Alycia Weinberger were selected for the inaugural class of Fellows of the American Astronomical Society in recognition of their “extraordinary achievement and service” to the field. 

The newly established accolade will honor members of the organization for original research, innovative technique and instrumentation development, significant public outreach and educational efforts, and other noteworthy contributions to the society. To launch the program, the AAS selected 200 “legacy” fellows, including Shectman and Weinberger. Carnegie trustee Sandra Faber of UC Santa Cruz and former-

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The fund supports a postdoctoral fellowship in astronomy that rotates between the Carnegie Science departments of Terrestrial Magnetism in Washington, D.C., and the Observatories in Pasadena California. 

The Earthbound Planet Search Program has discovered hundreds of planets orbiting nearby stars using telescopes at Lick Observatory, Keck Observatory, the Anglo-Australian Observatory, Carnegie's Las Campanas Observatory, and the ESO Paranal Observatory.  Our multi-national team has been collecting data for 30 years, using the Precision Doppler technique.  Highlights of this program include the detection of five of the first six exoplanets, the first eccentric planet, the first multiple planet system, the first sub-Saturn mass planet, the first sub-Neptune mass planet, the first terrestrial mass planet, and the first transit planet.Over the course of 30 years we have

The Giant Magellan Telescope will be one member of the next class of super giant earth-based telescopes that promises to revolutionize our view and understanding of the universe. It will be constructed in the Las Campanas Observatory in Chile. Commissioning of the telescope is scheduled to begin in 2021.

The GMT has a unique design that offers several advantages. It is a segmented mirror telescope that employs seven of today’s largest stiff monolith mirrors as segments. Six off-axis 8.4 meter or 27-foot segments surround a central on-axis segment, forming a single optical surface 24.5 meters, or 80 feet, in diameter with a total collecting area of 368 square meters. The GMT

Along with Alycia Weinberger and Ian Thompson, Alan Boss has been running the Carnegie Astrometric Planet Search (CAPS) program, which searches for extrasolar planets by the astrometric method, where the planet's presence is detected indirectly through the wobble of the host star around the center of mass of the system. With over eight years of CAPSCam data, they are beginning to see likely true astrometric wobbles beginning to appear. The CAPSCam planet search effort is on the verge of yielding a harvest of astrometrically discovered planets, as well as accurate parallactic distances to many young stars and M dwarfs. For more see

Evolutionary geneticist Moises Exposito-Alonso joined the Department of Plant Biology as a staff associate in September 2019. He investigates whether and how plants will evolve to keep pace with climate change by conducting large-scale ecological and genome sequencing experiments. He also develops computational methods to derive fundamental principles of evolution, such as how fast natural populations acquire new mutations and how past climates shaped continental-scale biodiversity patterns. His goal is to use these first principles and computational approaches to forecast evolutionary outcomes of populations under climate change to anticipate potential future

Staff Associate Kamena Kostova joined the Department of Embryology in November 2018. She studies ribosomes, the factory-like structures inside cells that produce proteins. Scientists have known about ribosome structure, function, and biogenesis for some time. But, a major unanswered question is how cells monitor the integrity of the ribosome itself. Problems with ribosomes have been associated with diseases including neurodegeneration and cancer. The Kostova lab investigates the fundamental question of how cells respond when their ribosomes break down using mass spectrometry, functional genomics methods, and CRISPR genome editing.

Kostova received a B.S. in Biology from the

Sally June Tracy applies cutting-edge experimental and analytical techniques to understand the fundamental physical behavior of materials at extreme conditions. She uses dynamic compression techniques with high-flux X-ray sources to probe the structural changes and phase transitions in materials at conditions that mimic impacts and the interiors of terrestrial and exoplanets. She is also an expert in nuclear resonant scattering and synchrotron X-ray diffraction. She uses these techniques to understand novel behavior at the electronic level.  Tracy received her Ph.D. from the California Institute of

The Ludington lab investigates complex ecological dynamics from microbial community interactions using the fruit fly  Drosophila melanogaster. The fruit fly gut carries numerous microbial species, which can be cultured in the lab. The goal is to understand the gut ecology and how it relates to host health, among other questions, by taking advantage of the fast time-scale and ease of studying the fruit fly in controlled experiments.