Artist's concept of Viking lander on Martian surface

F. VIKING LANDER MISSIONS (1976)

• Most ambitious robot space mission to that time. Two separate, nearly identical, spacecraft each consisting of an orbiter and a lander component. Orbiters mapped some 99% of Martian surface
  • Click here for a Viking Project fact sheet.

• Very sophisticated landers (though no rovers), taking weather & soil samples (shallow) at two sites

• Performed lab tests for organisms:
  • Organic molecules

  • Metabolism (solid ===> gas)

  • Photosynthesis (gas ===> solid)

  • Respiration (gas ===> gas)

• Results:
  • Iron-rich minerals; iron oxides (rust) produce red soil color

  • No organics; "strange" chemistry, but no biological activity

  • Soil samples only about 10cm deep; surface may be sterilized by solar UV and not representative

G. MARS PATHFINDER MISSION (1997)

• First of a new series of moderate-cost Martian orbiters and landers leading up to robot missions to return soil & rock samples to Earth.

• Novel airbag cushions permit landing without usual powerful (& heavy) retro-rockets. Here is an animation of how these work.

• Study atmosphere, soil, rocks on Ares Vallis, a floodplain region. First robot "rover" to sample rocks/soil distant from lander.

• Uses Alpha-Proton-X-ray Spectrometer to determine mineral content of rocks.

• Results: pebble & rock shapes give strong evidence for catastrophic floods. Possible sedimentary rocks, likewise. Minerals rich in quartz suggest differentiated interior. Dynamical evidence for iron core, implying hot, active interior at early times. General picture is more Earth-like than earlier thought, with perhaps long "wet-era" with stable liquid water on surface.

H. MARS EXPLORATION ROVER MISSION (2004)

• The MER mission consists of two landers with rovers, "Spirit" and "Opportunity," launched in mid-2003, which landed on Mars in January 2004.
  Click here for QuickTime animations of the launch and landing sequences of the MER mission.

• Landing sites were both chosen for their potential to demonstrate the presence of water on Mars in the past: Gusev Crater (Spirit) is a possible ancient lake bed; Meridiani Planum (Opportunity) is a plain with signs of a water-deposited mineral (hematite).

• Both sites have yielded strong evidence of a watery past on Mars by detecting traces of minerals which are produced in a water-rich environment and layering which is expected for rocks laid down at the edge of a lake or ocean.

I. "SNC" METEORITES

• Unanticipated source of info: a rare class of meteorite (24/20,000). Found in Antarctic meteorite fields.

• = Fragments of MARS ejected by asteroid impact
  • 1-2 Byr old; note that unprocessed remnants of the solar nebula would be much older (4.5 Byr)

  • Isotopes match Viking results

• Minerals show Mars once very WET. Water several 100 meters deep (global). Supports Pathfinder & imaging evidence for massive water flows.

• SNC (Martian) Meteorite ALH 84001; over 3.5 Byr old

• Contains evidence of microorganisms (August 1996 +)
  • Carbonate inclusions. "PAH" molecules ===> biosynthesis?

  • Microfossils (0.0001 mm) (see image at right; click for an enlarged view)

• ===> BACTERIAL LIFE MAY HAVE EXISTED on Mars
  during the "wet era", 1-4 Byr ago

• But interpretation of meteorite results is controversial. See the Lunar & Planetary Institute web site for links discussing various sides of the debate.

K. MARTIAN SATELLITES

• 2 satellites: Phobos & Deimos, discovered 1877

• Small (10-17 mi), irregular

• Captured asteroids

L. EXPEDITIONS TO MARS

Serious proposals for human expeditions to Mars have been around for over 50 years. In January 2004, President Bush proposed a long term commitment (20+ years) to a program that would send expeditions back to the Moon and ultimately to Mars.
Human space missions are much more costly than the robot craft we have used for all previous studies of Mars because of the life support systems needed (both during the trip and once on Mars' surface). However, many people are eager to go---for both scientific and personal reasons---and are exploring the various necessary technologies. There is much discussion of "terraforming" Mars---i.e. making it suitable for human colonies by releasing trapped water onto its surface and generating oxygen for an atmosphere.
The Moon/Mars initiative is controversial. Here is a link to a NASA Watch forum on the subject.
Click here for an article on a group experimenting with a Mars habitation module.

Artist's concept of human expedition to Valles Marinaris.

Seeds textbook: 22.2 and 22.3
Study Guide 17

H. G. Wells War of the Worlds
Study Guide 18

Study Guide 16 (Mars I, including general links)
Selected Mars Images (RWO)
Viking Mission
Pathfinder Mission
Mars Exploration Rover Mission
Meteorites from Mars (NASA/JSC)
SNC Meteorites Links Page (JPL)
SNC Meteorite Analysis (Eric Weisstein)
Critical Discussion of Martian Meteorite/Life Science
Discussion of Terraforming (Wikipedia)
Red Colony, one of many websites devoted to space colonization