Mark Robert Showalter (born December 5, 1957) is a Senior Research Scientist at the

SETI Institute The SETI Institute is a not-for-profit research organization incorporated in 1984 whose mission is to explore, understand, and explain the origin and nature of life in the universe, and to use this knowledge to inspire and guide present and futu ...

. He is the discoverer of six moons and three planetary rings. He is the Principal Investigator of NASA's

Planetary Data System The Planetary Data System (PDS) is a distributed data system that NASA uses to archive data collected by Solar System missions. The PDS is an active archive that makes available well documented, peer reviewed planetary data to the research communi ...

Rings Node, a co-investigator on the

Cassini–Huygens ''Cassini–Huygens'' ( ), commonly called ''Cassini'', was a space research, space-research mission by NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a space probe to study the planet Saturn and its system, i ...

mission to

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

, and works closely with the

New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research ...

mission to

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...

Biography

Showalter was born in Abington, Pennsylvania. He enjoyed playing with science-themed toys while a child, and later mowed lawns as a teenager so that he might purchase a

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

in high school. He received a

Bachelor of Arts Bachelor of arts (BA or AB; from the Latin ', ', or ') is a bachelor's degree awarded for an undergraduate program in the arts, or, in some cases, other disciplines. A Bachelor of Arts degree course is generally completed in three or four years ...

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

and

mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...

from

Oberlin College Oberlin College is a Private university, private Liberal arts colleges in the United States, liberal arts college and conservatory of music in Oberlin, Ohio. It is the oldest Mixed-sex education, coeducational liberal arts college in the United S ...

in 1979. He was initially undecided about pursuing a career in

astronomy Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...

after his undergraduate education, but made up his mind after seeing the images of Jupiter sent back to Earth by

Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, ''Voyager 1'', on a ...

. Showalter received his MS in

from

Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to teach an ...

in 1982, and his

PhD PHD or PhD may refer to: * Doctor of Philosophy (PhD), an academic qualification Entertainment * '' PhD: Phantasy Degree'', a Korean comic series * ''Piled Higher and Deeper'', a web comic * Ph.D. (band), a 1980s British group ** Ph.D. (Ph.D. albu ...

from Cornell in 1985. His thesis was on

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

ring system A ring system is a disc or ring, orbiting an astronomical object, that is composed of solid material such as dust and moonlets, and is a common component of satellite systems around giant planets. A ring system around a planet is also known as ...

, in which he discovered the gossamer ring of Jupiter. In 1990, using ten-year-old Voyager data, Showalter discovered Pan, the eighteenth and innermost

moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

of Saturn. It orbits within and keeps open the

Encke Gap The rings of Saturn are the most extensive ring system of any planet in the Solar System. They consist of countless small particles, ranging in size from micrometers to meters, that orbit around Saturn. The ring particles are made almost entirel ...

in Saturn's rings via shepherding. In 2003, Showalter and

Jack J. Lissauer Jack Jonathan Lissauer (born 1957) is an American research scientist who has worked for NASA's Ames Research Center since 1996. He is a science co-investigator on the Kepler space telescope mission. Biography Lissauer received a PhD in mathemat ...

discovered two new moons of

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus (mythology), Uranus (Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars (mythology), Mars), grandfather ...

(

Mab A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a cell Lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell. Monoclonal antibodies ca ...

and

Cupid In classical mythology, Cupid (Latin Cupīdō , meaning "passionate desire") is the god of desire, lust, erotic love, attraction and affection. He is often portrayed as the son of the love goddess Venus (mythology), Venus and the god of war Mar ...

) in

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

images. In 2006, they announced the discovery of two very faint rings, the μ and ν rings, within the same data. In 2010, Showalter discovered that spiral vertical corrugations in Jupiter's rings were caused by the impact of

Comet Shoemaker–Levy 9 Comet Shoemaker–Levy 9 ( formally designated D/1993 F2) broke apart in July 1992 and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of Solar System objects. This generated a l ...

in July 1994. A second smaller set of corrugations appear to be consistent with an unknown impact in early 1990. He and co-researchers also found similar spiral patterns in Saturn's D Ring. Showalter has assisted the New Horizons team in determining what hazards the spacecraft would encounter as it flew close to Pluto. A search for faint dust rings of Pluto using the Hubble Space Telescope in 2011 led to the discovery of the fourth moon Kerberos. Working with the New Horizons team, Showalter found the fifth moon

Styx In Greek mythology, Styx (; grc, Στύξ ) is a river that forms the boundary between Earth (Gaia) and the Underworld. The rivers Acheron, Cocytus, Lethe, Phlegethon, and Styx all converge at the centre of the underworld on a great marsh, whic ...

in July 2012. On July 15, 2013, a team of astronomers led by Showalter discovered a previously unknown fourteenth moon of Neptune in images taken by the Hubble Space Telescope from 2004 to 2009. Unnamed at that time,

Hippocamp The hippocampus or hippocamp, also ''hippokampos'' (plural: hippocampi or hippocamps; grc, ἱππόκαμπος, from , "horse" and , "sea monster"

is thought to measure around 34.8 km in diameter. Showalter was the 2021 recipient of the Harold Masursky Award for Meritorious Service to Planetary Science. The Mars-crossing asteroid 18499 Showalter is named after Dr. Showalter.

Personal life

Showalter is an avid

scuba diver Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface air supply. The name "scuba", an acronym for "Self-Contained Underwater Breathing Apparatus", was coined by Chris ...

and

photographer A photographer (the Greek language, Greek φῶς (''phos''), meaning "light", and γραφή (''graphê''), meaning "drawing, writing", together meaning "drawing with light") is a person who makes photographs. Duties and types of photographe ...

. He is married to Frank Yellin; they live in California.

Notes

References

External links

Mark Showalter's SETI Institute home page

Planetary Data System rings node home page
* Saturn's Restless Rings: Results from the Cassini Mission * Pluto on the Horizon: Anticipating our First Encounter with the Double Planet {{DEFAULTSORT:Showalter, Mark R. 1957 births People from Abington Township, Montgomery County, Pennsylvania Oberlin College alumni Cornell University alumni American astronomers Discoverers of moons Discoverers of astronomical objects Living people New Horizons Planetary scientists