• THOR Imaging Spectrometer
  • Launch: October 2011
  • Arrival: September 2012
  • Currently: Not selected

What is THOR?

THOR (Trace Habitability, Organics, and Resources) was a mission submitted to the Mars Scout Program (a NASA initiative to send a series of small, low-cost robotic missions to Mars). The program was retired in 2010, and THOR was not selected. THOR would have been the first mission to access the deep subsurface of Mars.

What does it do?

After launch in October 2011 and arrival at Mars in September 2012, THOR would have delivered two high-velocity impactors to excavate the ground and expose subsurface water ice. Under solar warmth, ice exposed by the impacts would turn into vapor, and THOR would determine the composition and abundance of key elements within the vapor cloud. THOR would then enter Martian orbit and both monitor the craters’ evolution and investigate the Martian atmosphere’s composition with unprecedented precision.

Why is it Significant?

THOR’s subsurface impact science and atmospheric observations would have provided a go-anywhere, low-risk approach to assess habitability on Mars. Previous surface missions have explored equatorial regions where water was once present, but is no longer stable. THOR would have bridged this gap, exploring potential habitable zones where liquid water exists today.


  • Determine the abundance of water in the deep Martian subsurface where ice can be stable
  • Determine the abundance and origin of key trace gases, including CH4 , SO2 , and CO
  • Test models of cyclic climatic change and the recent occurrence of liquid water
  • Search for organic compounds in habitable zones
  • Monitor the current climate through measurements of atmospheric water, dust, and CO2
  • Study the mineralogy of aqueous environments
The Mars Scout Program was a NASA initiative to send a series of small, low-cost robotic missions to Mars, competitively selected from innovative proposals by the scientific community. The program had an array of missions destined to reach Mars, and study it at relatively low costs. The Phoenix lander and MAVEN orbiter were selected and developed before the program was retired in 2010.

Meet the Group

Principal Investigator

  • Philip Christensen
  • Arizona State University

Participating Scientists

  • Raymond Arvidson
  • Washington University
  • Martin Chamberland
  • Telops
  • Benton Clark
  • Lockheed Martin Space Systems
  • Jack Farmer
  • Arizona State University
  • Victoria Hamilton
  • University of Hawaii
  • Susan Kieffer
  • University of Illinois
  • Jonathan Lunine
  • University of Arizona
  • Michael Malin
  • Malin Space Science Systems
  • Michael Mellon
  • University of Colorado
  • Lynn Rothschild
  • NASA Ames Research Center
  • Michael Smith
  • NASA Goddard Space Flight Center
  • Michael Wolf
  • Space Science Institute
  • Richard Zurek
  • NASA Jet Propulsion Laboratory

THOR's Mission Team

  • Robert Braun
  • Georgia Institute of Technology
  • Robert Burnham
  • Arizona State University
  • Greg Mehall
  • Arizona State University