ASTR 1010 1st EditionLecture 18Outline of Last Lecture I. Lunar FeaturesA. MariaB. CratersII. Origin of the Earth & MoonOutline of Current LectureI. Mercury & The MoonA. SimilaritiesB. DifferencesII. VenusA. PropertiesCurrent LectureI. The Moon & MercuryA. Similarities.- Small Masses- Moon: 0.012 Mass of Earth- Mercury: 0.055 Mass of Earth- Small Sizes- Moon: 0.27 Radius of Earth- Mercury: ).36 R Earth- Low Escape Speeds- Moon: 2.4 km/s- Mercury: 4.2 km/s- Highly cratered surfaces- No atmosphere (other than temporarily attracted solar winds.)- Large Temperature Swings- Moon: 100 – 400K- Mercury: 100-700K (Largest variation of all- Rotation and revolution locked in resonances (spin orbit resonance)- Moon: 1.1- Mercury: 3.2- Either no magnetic field (Moon) Or an extremely weak one (Mercury)B. Differences- Density- Moon: 3.3 g / cm3, Mercury: 5.4 g/ cm3 (Similar to Earth & Venus)- Formation- Moon was probably formed by a collision of a large planet (Maybe Mars’ size)- Mercury’s formation was probably similar to Earth’s Venus’ and Mars’ formation.II. VenusA. Properties- Atmosphere: CO2 rich, H2O, acids (Sulfuric, hydrochloric, hydrofluoric)- Temperature: 730K- Pressure: 100 Atms- Runaway Greenhouse Effect- High Speed Winds in Upper Atmosphere- Mass is 0.815 Earth’s Mass. (found via artificial satellites)- Radius is 0.95 of Earth- Density is 5.2 g / cm3- As seen from Earth:- Venus’ surface is invisible in the invisible band, completely shrouded in clouds- It is always within 47 degrees of the Sun. greatest elongation, so it never is seen more than 3 hours after dusk or 3 hours before dawn- Rotational Period/Sidereal Day: R = -243.0 days- Orbital Period: P = 224.7 days- Solar Day: D = 116.7
View Full Document
Unlocking...