{{Short description|American research scientist (born 1957)}} {{Infobox scientist | name = Mark R. Showalter | image = MarkRShowalter.jpg | caption = | birth_name = Mark Robert Showalter | birth_date = {{birth date and age|1957|12|05|mf=y}} | birth_place = [[Abington Township, Montgomery County, Pennsylvania|Abington, Pennsylvania]], U.S. | death_date = | death_place = | education = | alma_mater = [[Oberlin College]] (B.A.); [[Cornell University]] (M.Sc.), (Ph.D.) | field = [[Astronomy]], [[astrophysics]], [[space science]], [[planetary science]] | work_institutions = [[SETI Institute]] | known_for = Discoverer or co-discoverer of Jovian gossamer ring, Saturnian moon [[Pan (moon)|Pan]], Uranian moons [[Mab (moon)|Mab]] and [[Cupid (moon)|Cupid]], Uranian rings μ and ν, Neptunian moon [[Hippocamp (moon)|Hippocamp]], Plutonian moons [[Kerberos (moon)|Kerberos]] and [[Styx (moon)|Styx]] | prizes = | spouse = Frank Yellin }}
'''Mark Robert Showalter''' (born December 5, 1957) is an American senior research scientist at the [[SETI Institute]].<ref>{{Cite web |last=Boyle |first=Alan |title=Pluto's fifth moon discovered |publisher=[[MSNBC.com]] |date=2012-07-11 |url=http://cosmiclog.msnbc.msn.com/_news/2012/07/11/12683467-plutos-fifth-moon-discovered |accessdate=2012-07-16 |url-status=dead |archiveurl=https://web.archive.org/web/20120715042657/http://cosmiclog.msnbc.msn.com/_news/2012/07/11/12683467-plutos-fifth-moon-discovered |archivedate=2012-07-15 }}</ref> He is the discoverer of six moons and three planetary rings. He is the Principal Investigator of NASA's [[Planetary Data System]] Rings Node, a co-investigator on the [[Cassini–Huygens]] mission to [[Saturn]], and works closely with the [[New Horizons]] mission to [[Pluto]].<ref name="Bio"> {{Cite web |title = Mark Showalter's Home Page |work = Rings Node, NASA Planetary Data System |date = July 2012 |url = http://pds-rings.seti.org/showalter/ |accessdate = 2012-07-16 |url-status = dead |archiveurl = https://web.archive.org/web/20080917215555/http://pds-rings.seti.org/showalter/ |archivedate = 2008-09-17 }}</ref>
==Biography== Showalter was born in [[Abington Township, Montgomery County, Pennsylvania|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]] in high school. He received a [[Bachelor of Arts]] in [[physics]] and [[mathematics]] from [[Oberlin College]] in 1979. He was initially undecided about pursuing a career in [[astronomy]] after his undergraduate education, but made up his mind after seeing the images of Jupiter sent back to Earth by [[Voyager 2]].<ref name="Bio2"> {{Cite web | last = Tanner | first = Steve | title = SETI Institute's Ring Leader | work = San Jose Business Journal | date = 2007-01-07 | url = http://www.bizjournals.com/sanjose/stories/2007/01/08/smallb1.html | accessdate = 2012-07-16 }}</ref>
Showalter received his [[Master of Science|MS]] in [[astronomy]] from [[Cornell University]] in 1982, and his [[Doctor of Philosophy|PhD]] from Cornell in 1985.<ref name="Bio2" /><ref>{{cite web|url=https://astro.cornell.edu/people/phds.php |title=Cornell University Department of Astronomy Ph.D. recipients |url-status=dead |archiveurl=https://web.archive.org/web/20120710183313/http://astro.cornell.edu/people/phds.php |archivedate=2012-07-10 }}</ref> His thesis was on [[Jupiter]]'s [[Planetary ring|ring system]], in which he discovered [[Rings of Jupiter|the gossamer ring of Jupiter]].{{refn | At the time of discovery, the gossamer ring was thought to be a single ring. Later observations have resolved the gossamer ring into two separate, overlapping rings: the Thebe gossamer ring and the Amalthea gossamer ring. | group=lower-alpha}}<ref>{{cite journal|last1=Showalter|first1=Mark |last2=Burns |last3=Cuzzi |last4=Pollack |title=Discovery of Jupiter's 'gossamer' ring|journal=Nature|date=August 8, 1985|volume=316|pages=526–528|bibcode = 1985Natur.316..526S |doi = 10.1038/316526a0|pmid=11536560 |issue=6028|s2cid=4281782 |url=https://zenodo.org/record/1233033}}</ref>
In 1990, using ten-year-old [[Voyager program|Voyager]] data, Showalter discovered [[Pan (moon)|Pan]], the eighteenth and innermost [[Moons of Saturn|moon]] of Saturn. It orbits within and keeps open the [[Encke Gap]] in Saturn's rings via shepherding.<ref>{{cite journal|last=Showalter|first=Mark R|title=Visual detection of 1981S13|journal=Nature|date=27 June 1991|volume=351|pages=709–73|bibcode = 1991Natur.351..709S |doi = 10.1038/351709a0|issue=6329|s2cid=4317496}}</ref><ref name="Gazeteer"> {{Cite web | title = Gazetteer of Planetary Nomenclature | work = International Astronomical Union Working Group for Planetary System Nomenclature | publisher = Astrogeology Science Center, [[United States Geological Survey]] | date = 2006-07-21 | url = https://planetarynames.wr.usgs.gov/Page/Planets | accessdate = 2012-07-16 }}</ref>
In 2003, Showalter and [[Jack J. Lissauer]] discovered two new moons of [[Uranus]] ([[Mab (moon)|Mab]] and [[Cupid (moon)|Cupid]]) in [[Hubble Space Telescope]] images.<ref name="Gazeteer" /><ref>{{cite book|title=Solar System Moons: Discovery and Mythology|first=Jürgen |last=Blunck |publisher=Dordrecht |date=2010 |isbn=9783540688525 |pages=95}}</ref> In 2006, they announced the discovery of two very faint rings, the μ and ν rings, within the same data.<ref>{{cite journal|last=Showalter|first=Mark R|author2=Lissauer|journal=Science|date=17 February 2006|volume=311|pages=973–977|bibcode = 2006Sci...311..973S |doi = 10.1126/science.1122882|pmid=16373533|issue=5763|title=The second ring-moon system of Uranus: discovery and dynamics|s2cid=13240973|doi-access=free}}</ref><ref>{{cite book|title=Interplanetary Dust|url=https://archive.org/details/interplanetarydu00fech|url-access=limited|first=Eberhard |last=Grün |publisher=Springer |date=2001 |isbn=3540420673 |pages=[https://archive.org/details/interplanetarydu00fech/page/n688 668]}}</ref>
In 2010, Showalter discovered that spiral vertical corrugations in Jupiter's rings were caused by the impact of [[Comet Shoemaker–Levy 9]] 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.<ref>{{Cite web | last = Mason | first = J. | author2 = Cook, J.-R. C. | title = Forensic sleuthing ties ring ripples to impacts | work = [[Space Science Institute|CICLOPS]] press release | publisher = Cassini Imaging Central Laboratory for Operations | date = 2011-03-31 | url = http://www.ciclops.org/view.php?id=6762 | accessdate = 2011-04-04 | archive-date = 2011-05-30 | archive-url = https://web.archive.org/web/20110530095933/http://www.ciclops.org/view.php?id=6762 | url-status = dead }}</ref><ref>{{Cite web | author = NASA | author-link = NASA | title = Subtle Ripples in Jupiter's Ring | work = PIA 13893 caption | publisher = NASA / Jet Propulsion Laboratory-Caltech / SETI | date = 2011-03-31 | url = http://www.ciclops.org/view/6760/Subtle_Ripples_in_Jupiters_Ring | accessdate = 2011-04-04 | archive-date = 2014-04-19 | archive-url = https://web.archive.org/web/20140419221526/http://www.ciclops.org/view/6760/Subtle_Ripples_in_Jupiters_Ring | url-status = dead }}</ref><ref> {{Cite journal | last1 = Showalter | first1 = M. R. | last2 = Hedman | first2 = M. M. | last3 = Burns | first3 = J. A. | title = The impact of comet Shoemaker-Levy 9 sends ripples through the rings of Jupiter | journal = [[Science (journal)|Science]] | volume = 332 | issue = 6030| pages = 711–3 | date = 2011 | doi = 10.1126/science.1202241 | bibcode = 2011Sci...332..711S | pmid=21454755 | s2cid = 27371440 }}</ref><ref>{{Cite web | last =Matson | first =John | title = A New Wrinkle: Comet Strikes in the 1980s and 1990s Left Ripples in Jupiter's and Saturn's Rings | work = Scientific American | publisher = | date = 2011-03-31 | url = https://www.scientificamerican.com/article.cfm?id=ring-ripples | accessdate = 2012-07-16 }}</ref>
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 (moon)|Kerberos]].<ref name="Gazeteer" /><ref>{{cite web | last = Showalter | first = M. R. |author2=Hamilton, D. P. | title = New Satellite of (134340) Pluto: S/2011 (134340) 1 | work = Central Bureau for Astronomical Telegrams | publisher = [[International Astronomical Union]] | date = 2011-07-20 | url = http://www.cbat.eps.harvard.edu/cbet/cbet002769.txt | accessdate = 2011-07-20}}</ref> Working with the New Horizons team, Showalter found the fifth moon [[Styx (moon)|Styx]] in July 2012.<ref name="Sanders 2012-07-11"> {{cite web | last = Sanders | first = Ray | date = 11 July 2012 | title = Hubble Space Telescope detects fifth moon of Pluto | publisher = [[Phys.org]] | url = http://phys.org/news/2012-07-hubble-space-telescope-moon-pluto.html | accessdate = 11 July 2012 }} </ref><ref> {{cite web | last = Overbye | first = Dennis | date = 20 July 2012 | title = Despite Downgrade, Pluto Adds to Entourage | work = [[New York Times]] | url = https://www.nytimes.com/2011/07/21/science/space/21pluto.html | accessdate = 2012-07-16 }} </ref>
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 (moon)|Hippocamp]] is thought to measure around 34.8 km in diameter.<ref>[http://www.skyandtelescope.com/news/Neptunes-Newest-Moon-215535121.html Beatty, Kelly. "Neptune's Newest Moon." ''Sky and Telescope.'' July 15, 2013.] Accessed 2013-07-17. {{webarchive|url=https://archive.today/20130716121048/http://www.skyandtelescope.com/news/Neptunes-Newest-Moon-215535121.html |date=July 16, 2013 }}</ref>
Showalter was the 2021 recipient of the [[Masursky Award|Harold Masursky Award for Meritorious Service to Planetary Science]].<ref>{{cite web |title=Harold Masursky Award for Meritorious Service to Planetary Science |url=https://dps.aas.org/prizes/masursky |website=American Astronomical Society |access-date=10 August 2021}}</ref>
The [[List of Mars-crossing minor planets|Mars-crossing]] asteroid [[18499 Showalter]] is named after Dr. Showalter.
==Personal life== Showalter is an avid [[Scuba diving|scuba diver]] and [[Photography|photographer]]. He is married to Frank Yellin; they live in California.<ref name="Bio" /><ref>{{cite web|title=Harvard-Radcliffe Class of 1980 - Class Notes|url=http://classes.harvard.edu/olc/pub/HAA/college/notes.jsp?chapter=61|archiveurl=https://web.archive.org/web/20081225025702/http://classes.harvard.edu/olc/pub/HAA/college/notes.jsp?chapter=61|archivedate=25 December 2008}}</ref>
==Notes== {{reflist | group = lower-alpha }}
==References== {{Reflist|30em}}
==External links== * [https://www.seti.org/our-scientists/mark-showalter Mark Showalter's SETI Institute home page] * [http://pds-rings.seti.org/ Planetary Data System rings node home page] * {{YouTube|X5zcrEze8L4|Silicon Valley Astronomy Lectures, November 12, 2008}} Saturn's Restless Rings: Results from the Cassini Mission * {{YouTube|KfODJpfS0fo|Silicon Valley Astronomy Lectures, Jan. 28, 2015}} Pluto on the Horizon: Anticipating our First Encounter with the Double Planet
{{New Horizons}} {{authority control}}
{{DEFAULTSORT:Showalter, Mark R.}} [[Category:1957 births]] [[Category:People from Abington Township, Montgomery County, Pennsylvania]] [[Category:Oberlin College alumni]] [[Category:Cornell University alumni]] [[Category:Discoverers of moons]] [[Category:Discoverers of astronomical objects]] [[Category:Living people]] [[Category:New Horizons]] [[Category:American planetary scientists]]