[Baps] Taylor Perron talk, Friday March 17

[Sarah Stewart-Mukhopadhyay]

Harvard Special Planetary Science Seminar

Friday, March 17
1:00  pm
Phillips Auditorium, 60 Garden St.

Oceans on Mars and Rain on Titan: The Role of Fluids in Shaping
Planetary Surfaces

Taylor  Perron,
University of California, Berkeley.

  Abstract:  Fluids  have  shaped  the  surfaces of both Mars and Titan,
  creating  many  landforms  that  bear a strong resemblance to those on
  Earth.  I describe two case studies that illustrate what we, as remote
  observers  with  some  knowledge of terrestrial surface processes, can
  learn  about  the  present  states and evolutionary histories of other
  bodies  by studying their surfaces. First, I present evidence that the
  formation  and  subsequent  disappearance  of  oceans  early  in Mars'
  history  significantly  affected  Mars'  global-scale  topography, and
  perhaps  even  influenced the planet's rotational stability. Second, I
  analyze dendritic valley networks near the landing site of the Huygens
  probe  on Titan, and obtain an estimate of the minimum rate of methane
  rainfall required to erode the valleys.

  Geologic  and  topographic  features  near the margins of the northern
  plains  of  Mars have been interpreted as shorelines formed by ancient
  oceans.  The  ocean hypothesis was called into question, however, when
  topographic  data  revealed that elevation profiles along the putative
  shorelines do not follow surfaces of equal gravitational potential, as
  the  margins  of  a  standing  body  of  water should. Long-wavelength
  (thousands  of  km) trends, with amplitudes of hundreds of meters, are
  especially  apparent  in  the  shoreline topography. I show that these
  topographic  trends  can  be  explained by deformation associated with
  true  polar  wander  (a  reorientation  of  Mars  with  respect to its
  rotation  axis),  and  that  the inferred true polar wander could have
  resulted from the redistribution of the ocean water.

  Branching  valley  networks near the landing site of the Huygens probe
  on  Titan  imply  that  flowing  fluid  has  eroded  the  surface. The
  morphology  of  the valley networks is most consistent with mechanical
  valley  erosion  by  methane  precipitation  and  surface  runoff.  If
  mechanical  erosion  did occur, the methane flows must first have been
  able  to  mobilize  any  sediment  accumulated  in  the valleys. I use
  sediment  transport  relations  scaled from Earth to Titan to estimate
  the  minimum  methane precipitation rate required to mobilize sediment
  and  initiate  erosion.  For  the sediment grain sizes observed at the
  Huygens landing site, the estimated precipitation rates are Earthlike,
  and  are  quite  plausible  given the large mass of methane in Titan's
  atmosphere  and  the  considerable  potential  for  the  formation  of
  convective storms.

Directions: http://www.cfa.harvard.edu/mapsdir.html
http://www.cfa.harvard.edu/calendar/latest.html

--
Sarah T. Stewart-Mukhopadhyay
Asst. Professor of Planetary Science
Dept. of Earth & Planetary Sciences, Harvard University
Office 617.496.6462 Lab 617.496.5782 Fax 617.496.7411
sstewart at eps.harvard.edu
http://www.fas.harvard.edu/~planets/sstewart/