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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Viking 2 | 2/2 | https://en.wikipedia.org/wiki/Viking_2 | reference | science, encyclopedia | 2026-05-05T13:26:26.695880+00:00 | kb-cron |
=== Search for life === Viking 2 carried a biology experiment whose purpose was to look for life. The Viking 2 biology experiment weighed 15.5 kg (34 lb) and consisted of three subsystems: the Pyrolytic Release experiment (PR), the Labeled Release experiment (LR), and the Gas Exchange experiment (GEX). In addition, independent of the biology experiments, Viking 2 carried a Gas Chromatograph/Mass Spectrometer (GCMS) that could measure the composition and abundance of organic compounds in the Martian soil. The results were unusual and conflicting: the GCMS and GEX gave negative results, while the PR and LR gave positive results. Viking scientist Patricia Straat stated in 2009, "Our (LR) experiment was a definite positive response for life, but a lot of people have claimed that it was a false positive for a variety of reasons." Many scientists believe that the data results were attributed to inorganic chemical reactions in the soil. However, this view may be changing due to a variety of discoveries and studies since Viking. These include the discovery of near-surface ice near the Viking landing zone, the possibility of perchlorate destruction of organic matter, and the reanalysis of GCMS data by scientists in 2018. Some scientists still believe the results were due to living reactions. The formal declaration at the time of the mission was that the discovery of organic chemicals was inconclusive. Mars has almost no ozone layer, unlike the Earth, so UV light sterilizes the surface and produces highly reactive chemicals such as peroxides that would oxidize any organic chemicals. The Phoenix Lander discovered the chemical perchlorate in the Martian soil. Perchlorate is a powerful oxidizing agent, which could have eradicated any organic material on the surface. Perchlorate is now considered widespread on Mars, making it hard to detect any organic compounds on the Martian surface.
=== Viking 2 lander image gallery ===
== Orbiter results ==
=== Viking program === The Viking Orbiters led to significant discoveries about the presence of water on Mars. Huge river valleys were found in many areas. They showed that water floods carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. In the southern hemisphere, the presence of branched stream areas suggests that there was once rainfall. The images below are mosaics of many small, high-resolution images.
== See also == Exploration of Mars List of missions to Mars List of Mars orbiters Timeline of artificial satellites and space probes U.S. Space Exploration History on U.S. Stamps Viking lander biological experiments
== Notes ==
== References ==
== External links == The Viking Mars Missions Education & Preservation Project, VMMEPP online exhibit. Viking 2 Mission Profile by NASA's Solar System Exploration 45 years ago: Viking 1 Touches Down on Mars