WASHINGTON — The National Academy of Sciences will honor three individuals with awards in recognition of their extraordinary scientific achievements in a variety of fields in the earth and space sciences.

Alexander J. Dessler, adjunct professor in the department of atmospheric sciences at Texas A&M University, is the recipient of the 2015 Arctowski Medal.

Dessler's research largely anticipated, and greatly enabled the analysis of, the major space-age discoveries about the heliosphere — the bubble surrounding the solar system where plasma motions are determined by the solar wind and its embedded interplanetary magnetic field. He was instrumental in developing the concept of the planetary magnetosphere — the comet-shaped cavity that surrounds planets such as Earth where the planet's magnetic field dominates rather than the solar wind. His 1960s vision of Earth's magnetosphere actually adorns the Arctowski Medal. In other work, Dessler elucidated the roles of MHD waves and of Birkeland currents in providing the communication and dynamic coupling between the solar wind, the magnetosphere, and the underlying planetary ionosphere. These interactions underlie dazzling polar auroras. And his analyses of the effects of the South Atlantic (magnetic) Anomaly on the structure and dynamics of the Van Allen radiation belts surrounding Earth proved crucial in subsequent studies of Jupiter's pulsar-like magnetosphere.

The Arctowski Medal is presented every two years to recognize outstanding contributions to the study of solar physics and solar terrestrial relationships. The medal is presented with an award of $20,000, plus $60,000 to support research in solar physics and solar terrestrial relationships.

Hiroko Nagahara, professor in the department of earth and planetary science at the University of Tokyo, is the recipient of the 2015 J. Lawrence Smith Medal.

Nagahara is being honored for her work on chondrites, the most abundant type of meteorite. While still a graduate student, she shed light on a mystery about the source of chondrules — tiny, round grains of minerals that are characteristic of chondrites. She showed that some chondrules contained grains that had survived melting, which indicated that those chondrules formed not from gas in the solar nebula, as some theorized, but from the incomplete melting of an already-solid material. Nagahara went on to introduce condensation and evaporation experiments into chondrite science. In the lab, she successfully condensed minerals that are known to form chondrites, such as silicate and metallic iron. In later theoretical and experimental work, Nagahara and colleagues elucidated the processes underlying condensation and evaporation in the early solar nebula, helping to deepen our understanding of how Earth and the solar system formed. 

The J. Lawrence Smith Medal is awarded every three years for investigations of meteoric bodies. The award includes a $50,000 prize. The award was established as a gift from Sarah Julia Smith in memory of her husband and has been presented since 1888.

Susan M. Kidwell, William Rainey Harper Professor in the department of the geophysical sciences and the committee on evolutionary biology at the University of Chicago, is the 2015 recipient of the Mary Clark Thompson Medal.

Kidwell has combined geological fieldwork, lab experiments, and measurements in modern environments to investigate how the fossil record is formed and how to best use it to understand the past and anticipate the future of biodiversity. In comparative analyses along environmental gradients and across geologic time, she determined the major controls on how and where marine life is preserved, providing a strategy for extracting the most reliable data from the fossil record. That opened new opportunities for discoveries about the ecology and evolution of ancient life. She showed that misfits between live populations and the seashells they leave behind on modern seafloors signal not poor preservation but a recent ecological shift, almost always driven by human activities such as pollution. This research has fostered a new field of science — conservation paleobiology — which uses the youngest part of the fossil record to determine the baseline condition of ecosystems and evaluate the effects humans have had on biodiversity.

Established in 1919 by a gift from Mary Clark Thompson to honor important services to geology and paleontology, this medal is presented every three years with a $15,000 prize.

The winners will be honored in a ceremony on Sunday, April 26, during the National Academy of Sciences' 152nd annual meeting.

The National Academy of Sciences is a private, nonprofit institution that was established under a congressional charter signed by President Abraham Lincoln in 1863. It recognizes achievement in science by election to membership, and — with the National Academy of Engineering, Institute of Medicine, and National Research Council — provides science, engineering, and health policy advice to the federal government and other organizations.

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