Planetary Geology

1. Planetary Geology

2. The Solar System in 1957 A half century ago, in 1957, most astronomers believed that there few discoveries left to be made in the Solar System Besides the Sun, there were the nine planets, the asteroid belt, comets and little else Saturn had rings and Mars was red...

3. The Solar System in 1957 Only a few astronomers were conducting research on the Solar System Most astronomers were looking beyond to the stars and galaxies The science of planetary geology was unheard of

4. Sputnik Then the space age began when the U.S.S.R. launched the Sputnik One satellite into orbit on October 4, 1957

5. Sputnik The surprise launch of Sputnik 1, coupled with the spectacular failure of the United States' first two Project Vanguard launch attempts, shocked the United States The space race began...

6. Apollo On May 25, 1961, President John F. Kennedy announced before a special joint session of Congress the dramatic and ambitious goal of sending an American safely to the Moon and back before the end of the decade

7. Apollo The Apollo missions to the Moon were a staggering success

8. The Solar System in 2010 In the 53 years since Sputnik, spacecraft have visited our Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune, several asteroids and comets This has revolutionized our view of the Solar System

9. The Nebular Hypothesis In cosmology, the Nebular Hypothesis is the currently accepted argument about how a Solar System can form

10. The Nebular Hypothesis Our sun and the planets formed at the same time, about 4.5 billion years ago, from a large rotating cloud of interstellar dust and gas called the solar nebula

11. The Nebular Hypothesis A large gas cloud (nebula) begins to condense Most of the mass is in the center and there is turbulence in the outer parts

12. The Nebular Hypothesis Gravitational attraction causes the mass of gas and dust to slowly contract and it begins to rotate The dust and matter slowly falls towards the center

13. Birth of the Solar System

14. Birth of the Solar System

15. Birth of the Sun After sufficient mass and density was achieved in the Sun, the temperature rose to one million °C, resulting in thermonuclear fusion H atom + H atom = He atom + energy

16. Sun The Sun has a diameter of about 1,392,000 kilometers (862,000 miles), about 109 times that of Earth Astronomers classify the spectral type of the Sun as G2 It has a surface temperature of about 5,500 oC The temperature in the center of the Sun is believed to be greater than 14 million degrees

17. Sun Because the Sun is not solid, but is composed of extremely hot gases, the time of rotation varies by latitude Latitude Time of Rotation Equator 25.05 days 16o 25.38 days Poles 34.4 Days

18. Sun The Sun contains about 99.86% of the total mass of the Solar System About three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium Less than 2% consists of heavier elements, including oxygen, carbon, neon, and iron

19. Sunspots The most common visible features on the Sun are sunspots, which appear darker than their surroundings because of lower temperatures The number of sunspots varies over an 11-year cycle

20. Sunspots & Solar Flares Sunspots are regions of intense magnetic activity where convection is inhibited by strong magnetic fields, reducing energy transport from the hot interior to the surface The largest sunspots can be tens of thousands of kilometers across (bigger than Earth)

21. Sunspots & Solar Flares The magnetic field causes strong heating in the corona, forming active regions that are the source of intense solar flares and coronal mass ejections

22. Aurora Borealis When the solar flares interact with the Earth’s magnetic field, they create the Aurora Borealis commonly called “northern lights” with similar displays occur over the South Pole

23. Sun The Sun is currently very stable and will be for another couple of billion years However, the process of thermonuclear fusion that energizes the Sun will eventually convert much of the hydrogen and helium into heavier elements In about 5-7 billion years, the Sun will evolve into a red giant and finally become a white dwarf

24. Solar Probe Plus “Solar Probe Plus will be an extraordinary and historic mission, exploring what is arguably the last region of the solar system to be visited by a spacecraft, the Sun’s outer atmosphere or corona as it extends out into space.” - JPL

25. Composition of the Planets Today, planetary geologist, divide the planets, moons, asteroids and comets into three major compositional groups, based upon their melting points (which, in turn, related as to where formation occurred in the Solar System) Rocks Gases Ices

26. The Four Terrestrial Planets In the inner solar system, the temperatures in the solar nebula were so high that only metals and silicate minerals could form solid grains It was too hot for gases and ices Thus, the four innermost (terrestrial) planets were mainly created from the high melting point substances found in the solar nebula

27. The Four Gas Giant Planets The four gas giant planets, Jupiter, Saturn, Uranus and Neptune are commonly called the Jovian planets The most obvious difference between the terrestrial and Jovian planets is size, with the Jovian planets being much larger

28. The Four Gas Giant Planets In the outer solar system, the temperatures in the solar nebula were low and both gases and ices could exist (along with solid mineral grains) So, the outer planet grew not only from rock debris that came from the inner solar system, but also ices and especially gases

29. The Four Gas Giant Planets Eventually, the outer planet became so large that they were able to capture large quantities of light gases such as hydrogen and helium They grew in size into the gas giants

30. Birth of the Solar System Beyond Neptune, ice and frozen gases formed Pluto and the Kuiper Belt Objects, such as Sedna Left-over debris formed comets and asteroids

31. Birth of the Solar System We now know that in the far outer reaches of the Solar System that there probably thousands (perhaps millions or billions) of dwarf planets and comets composed primarily of ices These include the so-called Kuiper Belt Objects

32. The Eight Planets Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune According to the International Astronomical Union, there are now eight planets

33. Planet Vulcan? Planet Vulcan, aside from being the fictional planet in Star Trek which Spock comes from, is a hypothetical planet that many astronomers in the 19th century believed to exist This planet was supposed to have a low mass and be closer to the Sun than Mercury A few astronomers claimed to have observed Vulcan transiting the Sun .

34. Planet Vulcan? The reason astronomers inferred that Planet Vulcan existed was due to discrepancies in the orbit of Mercury, detected by the French mathematician Urbain Jean Joseph Le Verrier in 1840-1843 when he was trying to predict the planet's motion based on Newtonian math All orbits change with time, the problem was that Mercury’s orbit changed more than calculated The presence of another planet (more mass) would explain the discrepancies

35. Planet Vulcan ... No But nobody could find Vulcan Albert Einstein used his General Theory of Relativity, which was announced in 1915, to precisely explained the anomaly as a by product of the Sun's gravitational field Simply put, the mass of the Sun curves the space time continuum around Mercury Einstein’s explanation is considered to be the first great proof of the General Theory of Relativity

36. Mercury Mercury is the inner most planet It is the smallest of the eight planets, with a diameter of 4878 kilometers (3015 miles) Physically, Mercury is very similar in appearance to our Moon, because it is heavily cratered It has no moons and no atmosphere

37. Mercury Mercury orbits the Sun once every 88 days In addition, Mercury rotates once every 59 days, which means that the orbital period and rotational period are in a “3:2 resonance” Therefore, a full day-night-cycle takes 176 Earth days on Mercury

38. Mercury Mercury is only 37 million miles (57.9 million kilometers) from the sun Therefore, the Sun appears 10 times larger At “high noon”, the surface temperature on Mercury reaches 430oC (800oF)

39. Mercury Mercury has a stable magnetic field, but it is only 1% as strong as the Earths

40. Mercury Back in the mid-1970s, Mariner 10 was the first spacecraft to fly by Mercury (actually it flew by 3 times) Mariner confirmed that Mercury is a small, airless planet comparable in appearance to our Moon

41. Mercury In August 2004, NASA launched the Messenger Spacecraft to Mercury It has flown by Mercury three times and will go into orbit around the planet in March 2011

42. Mercury Photography both in color and B&W

43. Messenger at Mercury The blue dots indicate the spacecraft ground track, and the yellow dots show the variation in elevation measured by the spacecraft’s laser altimeter The deeper crater in the center of the track is Machaut crater

44. Venus of Mystery As seen through telescopes on Earth, Venus is shrouded in thick clouds impenetrable to visible light It was a planet of mystery

45. Venus of Mystery Venus is essentially the same size as Earth and obviously has an atmosphere It was called “Earth’s sister” Many scientists thought the planet might harbor life Science fiction writers populated the planet with flying aliens and great oceans and other fanciful things

46. The Real Venus A series of pictures of the surface of Venus were taken by four different U.S.S.R. Venera spacecraft between 1975-1982 The surface of Venus was absolutely lifeless

47. The Real Venus In the early 1990s, using imaging radar, the U.S. Magellan spacecraft mapped over 98% of the surface of Venus from orbit The radar was able to see thru the thick atmosphere and provided detailed, computer generated maps that revealed the hidden surface

48. The Real Venus About 80% of the Venus surface consists of subdued plains that are covered with lava flows Thousands of volcanic structures have been identified, most are small shield volcanoes, but more than 1500 large volcanoes have also been catalogued The volcano in the foreground, Sapas Mons, is about 400 kilometers in diameter

49. Venus, the Greenhouse Planet Worse, the thick, opaque atmosphere of Venus has created an environment akin to hell Clouds are revealed when Venus is photographed in the ultraviolet by orbiting spacecraft

50. Venus, the Greenhouse Planet The atmosphere of Venus is over 200 kilometers thick It is composed of 96.5% carbon dioxide (CO2) with clouds of sulfuric acid The average surface temperature is 460oC (860oF) The atmospheric pressure on the surface of Venus is 92 times that of the Earth There is no water on Venus