=== Sample tests ===
 * http://soinc.org/solar_b
 * Soinc solar system sample tests
  * 14-15 https://www.soinc.org/sites/default/files/uploaded_files/SOLAR_SYSTEM_ES_GUIDE_B15.pdf
  * 17-18 https://www.soinc.org/sites/default/files/uploaded_files/082317_SS1718_AnnotatedExampleExam.pdf https://www.soinc.org/sites/default/files/uploaded_files/082317_SS1718_ExampleExam.pdf
 * American Association of Variable Star Observers:
  * 2015 http://www.aavso.org/science-olympiad-2015
  * 2014 http://www.aavso.org/science-olympiad-2014 
 * https://scioly.org/wiki/index.php/2018_Test_Exchange
 * http://www.azscienceolympiad.org/uploads/2/2/0/1/22012620/solar_system_test.docx
=== Science Olympiad Mars references ===
 * https://quizlet.com/77850839/science-olympiad-2015-solar-system-info-mars-flash-cards/
=== Fact sheets ===
 * https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
 * https://www.jpl.nasa.gov/news/factsheets.php

=== General Solar system or Mars info ===
 * https://scioly.org/wiki/index.php/Solar_System https://scioly.org/wiki/index.php/Solar_System/Missions
 * NASA Mars overview https://solarsystem.nasa.gov/planets/mars
 * NASA Mars Exploration program https://mars.nasa.gov/
 * Space facts: https://space-facts.com/mars/
 * http://www.pbs.org/lifebeyondearth/alone/mars.html
 * Mars Facts: Life, Water and Robots on the Red Planet https://www.space.com/47-mars-the-red-planet-fourth-planet-from-the-sun.html
 * Mars research http://planetary-science.org/mars-research/

=== Mars atmosphere, climate, weather ===
 * https://www.space.com/16903-mars-atmosphere-climate-weather.html
 * https://en.wikipedia.org/wiki/Atmosphere_of_Mars

=== Mars Geologic properties ===
 * https://en.wikipedia.org/wiki/Geology_of_Mars