Transcript Mercury
Mercury Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mercury, The Innermost Planet • Mercury is one of the least explored planets in the Solar System – Makes it hard to observe because it NEVER gets more than 28º from the Sun’s glare. – Mariner 10 (1974) provided most of the information we have • flew by the planet (at 10,000 Km) and sent pictures back to Earth. • Mapped the whole planet – NASA’s MESSENGER mission returned to Mercury in 2011 for a more in-depth study. Mercury, The Innermost Planet • Planet of Extremes – On the dayside, surface temperatures is about 800.6 degrees F (427 C) – On the darkside, temperatures drop as low as -297 degrees F (-183 C) • THIS IS THE MOST EXTREME TEMPERATURE RANGE between night & day OF ALL PLANETS. – Mostly due to NO atmosphere • This causes the planet to shrink and swell. Mercury, The Innermost Planet • Planet “sort of” has an atmosphere • BUT not really: – thin helium,(also sodium, oxygen, potassium & hydrogen) Mercury, The Innermost Planet • Atmosphere is blown away by the Solar Wind of the Sun. This is because of: – Low gravity of mercury. – And… Mercury, The Innermost Planet • The sodium and oxygen particles the blistering solar wind kicks up are the primary components of Mercury's wispy atmosphere, or "exosphere,“ Mercury, The Innermost Planet • Through interacting with the solar wind, they become charged in a mechanism that's similar to the one that generates the Aurora Borealis on Earth. Mercury, The Innermost Planet • Planet of Extremes – Very eccentric orbit, coming as close as .29 AU and as far as 0.41 AU (.387 AU) • 1 AU = 93,000,000 miles – (from sun to earth) • Very elliptical orbit • 36,000,000 miles (35,991,000 miles) – Tilt of 28 degrees – Incline plane of 7 degrees Mercury, The Innermost Planet • Planet of Extremes – Rotation period – 58 days/15 min/28 sec (59 days) – spin on axis or day & night – Mercury rotates once every 58.647 days, which is exactly 2/3 of its orbital period of 87.970 days, so it turns on its axis exactly 1 1/2 times during one of its years, Mercury, The Innermost Planet • Planet of Extremes – Revolution period is 87.97 days (88 days) • Rotation is one and a half times for each orbit around the sun. • This means there are 3 days in every 2 years on Mercury • This is the 3:2 Synchronous orbit – Caused by: » Close to the Sun » Very eccentric orbit » High Density » Tidal Torque (pull from Sun) – Means the same side faces SUNWARD at perihelion • This makes it the MOST elliptical orbit of ANY major planet 3:2 Orbital Resonance • Mercury is tidally locked to the Sun – Similar to the way the Moon is tidally locked with the Earth – After one orbit around the Sun (88 days), the planet has rotated on its axis 1.5 times – It then takes two orbits for Mercury to rotate three times! 3:2 Orbital Resonance • Mercury is tidally locked to the Sun – Similar to the way the Moon is tidally locked with the Earth – After one orbit around the Sun (88 days), the planet has rotated on its axis 1.5 times – It then takes two orbits for Mercury to rotate three times! 3:2 Orbital Resonance • Mercury is tidally locked to the Sun – This is called a 3:2 orbital resonance – Sunrise and sunset are very strange on this planet! • The Sun actually undergoes retrograde motion through Mercury’s sky! Most likely resembles the Moon • Surface is covered with craters and lava flows • Fewer of the craters overlap • Craters are similar to the Moon’s, with rays and crater walls • Lower crater rims due to Mercury’s higher gravity • Early in Mercury’s history, a huge impact occurred on the surface Caloris Basin Caloris Basin • Formed an impact site known as the CALORIS BASIN Caloris Basin CALORIS BASIN It is a Large Basin that almost split planet in two. Planet hit with a 60 mile wide iron Meteor. Leaving the LARGEST CRATER IN THE S.S. Caloris Basin CALORIS BASIN 300Km (812.5miles) across and about 1 mile high Caloris Basin • The impact was so great that shock waves traveled through the planet and shook up the terrain on the opposite side! Caloris Basin • This created on the other side (opposite) where shock wave converged is known as WEIRD TERRAIN It formed about Kilometer or 2 per SECOND… Also there are Cliffs similar to earth (Valley) called: Scarps Scarps • Running across Mercury’s surface are scarps, kilometer-tall cliffs that are the result of the shrinking of the planet as it cooled • Scarps are similar to wrinkles in an apple’s skin that form as it dries • The presence of these cliffs suggests that the core of Mercury is large and metallic – something that would shrink significantly as it cools The Interior of Mercury • Mercury’s density is unusually high, 5.4 kg/liter • Indicates a very large iron core covered by a thin silicate mantle The Interior of Mercury • Sounds of the Planet https://www.youtube.com/watch?v =894Aejo-R0U The Interior of Mercury • Mercury may have a molten iron core, despite its size • This core may be the cause of the weak magnetic field (similar in shape to the Earth’s, but much weaker) Why is Mercury so dense? • It is possible that Mercury once had a thicker mantle, but a collision removed most of the material, leaving only the core and a little lighter mantle material behind Unit 38 Mercury Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.