Mars: History of Exploration III

1. Geography 441/541 S/18 Dr. Christine M. Rodrigue Mars: History of Exploration III C.M. Rodrigue, 2018 Geography, CSULB

2. C.M. Rodrigue, 2018 Geography, CSULB Mars: History of Mars Exploration History of Earth-based Mars exploration The Spectral Analysis era: A New Mars Spectral analysis in this context is the study of absorbed, emitted, and scattered/reflected radiation A radiant object can emit wavelengths along the EMS at varying intensities: hot or dense objects emit across a continuous spectrum Substances in the radiant object or between it and the sensor can absorb certain wavelengths The wavelengths absorbed are diagnostic of particular minerals or elements or compound Substances and surfaces also reflect particular wavelengths

3. Mars: History of Mars Exploration • History of Earth-based Mars exploration • The Spectral Analysis era: A New Mars • The electromagnetic spectrum (EMS) can be displayed by wavelength C.M. Rodrigue, 2018 Geography, CSULB

4. Mars: History of Mars Exploration • History of Earth-based Mars exploration • The Spectral Analysis era: A New Mars • Continuous spectra • Emission line spectra • Absorption line spectra C.M. Rodrigue, 2018 Geography, CSULB

5. Mars: History of Mars Exploration • History of Earth-based Mars exploration • The Spectral Analysis era: A New Mars • Some reflectance spectra in the near-infrared: • water • carbon dioxide • methane C.M. Rodrigue, 2018 Geography, CSULB

6. Mars: History of Mars Exploration • History of Earth-based Mars exploration • The Spectral Analysis era: A New Mars • Some reflectance spectra: • basalt (infrared) • common igneous rocks (VL-MIR) C.M. Rodrigue, 2018 Geography, CSULB

7. C.M. Rodrigue, 2018 Geography, CSULB Mars: History of Mars Exploration • History of Earth-based Mars exploration • The Spectral Analysis era: Martian air pressures • In 1862, Sir William Higgins tried out the new technology to get at Martian atmospheric pressures: All he got was that sunlight reflected off Mars and the planet didn’t glow • In 1867, he and Pierre Jules Jenssen took spectra of Mars to look for water vapor and oxygen and found none • In 1908, Percival Lowell also tried spectroscopy: • Mars’ air pressure looked like 87% of Earth’s • His method was sound, but he didn’t correct for dust • Erroneous as his results were, the method was a significant contribution to launching the use of spectral analysis on Mars and other planets

8. C.M. Rodrigue, 2018 Geography, CSULB Mars: History of Mars Exploration • History of Earth-based Mars exploration • The Spectral Analysis era: Martian temperatures • Any object that absorbs radiation re-emits it at a longer wavelength, because it is necessarily cooler than the original radiant body • Wien’s Displacement Law (L = 2,897 / TK) allows you to calculate temperatures (TK = 2,897 / L ) • In the 1920s, Lowell Observatory established that Mars was very cold, -40 C on average (Earth averages 15  C) • The poles got down around -70  C, and the equatorial areas got as warm as 10  C • In 1954, equatorial highs got as high as 25  C

9. C.M. Rodrigue, 2018 Geography, CSULB Mars: History of Mars Exploration • History of Earth-based Mars exploration • The Spectral Analysis era: Life on Mars? • Mars shows seasonally shifting patterns of spring darkening • Some folks inferred that this could be a wave of vegetation greening up for spring • In 1938, Peter Millman compared the spectra from the dark areas with spectra that had been collected for various kinds of vegetation here on Earth and said they did not resemble one another at all • In 1954, W.M. Sinton said these spectra did resemble organic compounds, later retracting this • Audoin Dofus and Thomas McCord showed that the dark areas were not greenish: That was an optical illusion