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

Caloris Basin• Early in Mercury’s history, a huge

impact occurred on the surface

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.