the terrestrial planets. earth mars venus mercury because the 4 inner planets have solid, rocky...
TRANSCRIPT
The Terrestrial
Planets
Earth
Mars
Venus
Mercury
Because the 4 inner planets have solid, rocky terrains…
Earth
Mars
Venus
Mercury
…they are sometimes called the “terrestrial planets”.
Earth
Mars
Venus
Mercury
Starting with Mercury, each planet will be discussed in detail.
Mercury
The “planet” Mercury was named for
the “Roman god” Mercury.
In Roman mythology, Mercury was the
god of trade and commerce.
The word, “merchant” contains the same root as the word, “Mercury”.
Mercury was also
the son of Jupiter.
Mercury is only slightly larger than the Earth’s Moon.
Earth
MercuryMoon
In order of planets away from the Sun, Mercury is the innermost planet.
Because it is so close to the Sun, it is often quite difficult to observe.
Here we see the Moon just after sunset.
Did you also notice Mercury in the sky?
Did you also notice Mercury in the sky?
Although Mercury is one of the brightest objects in the
sky…
…most people, have never seen it.
On his deathbed, for example, Galileo lamented the fact…
…that he was dying without ever having seen Mercury.
At its greatest elongation…
greatest elongation (aphelion)
28o
greatest elongation (aphelion)
…Mercury is never found more than 28o away from the Sun.
At its least elongation…
least elongation (perihelion)
…Mercury is only found at 18o away from the Sun.
least elongation (perihelion)
18o
This means that Mercury is never far from
the setting Sun.
This photo shows the highest position that Mercury reaches on various dates.
On February 8, Mercury is at its greatest elongation.
setting Sun
On this date, it should be 28o away from the setting Sun.
28o
Just like Venus and the Moon…
…Mercury also experiences a full cycle of phases.
Because only 2 of those phases are visible from Earth…
Mercury is only visible for about 1 week at a time, twice per year.
Recall that distances within the solar system…
…are measured in “astronomical units”.
And that 1astronomical unit…
…is the average distance from the Earth to the Sun.
1 AU
Mercury’s distance, on the other hand…
is found at only 0.39 AUs from the Sun.
0.39 AU
_______
This makes Mercury 2.5x closer to the Sun than
the Earth.
0.39 AU
1.00 AU
0.39 AU= 2.5 x closer
0.39 AU
(2.5)2 = 6.25 x bigger
In being 2.5x closer to the Sun, the Sun appears to be 6.25x
bigger.
If this is how big the Sun appears when viewed from Earth…
The Sun as seen from Earth
…then here’s how big the Sun appears when viewed from Mercury.
The Sun as seen from Earth
The Sun as seen from Mercury
6.25 x bigger
Rotation and
Revolution
rotation: counter-clockwise
North Pole
Mercury
equator
radio telescope(satellite dish)
Mercury’s rotation was
difficult to determine.
For one thing, it rotates very slowly.
Secondly, in being so close to the Sun, its surface is difficult to observe.
However, using the Doppler Effect, Mercury’s rotation was calculated.
same wavelengths
Identical radio waves leave the dish with the same wavelengths.
approaching side
From the approaching side, the returning waves are shorter.
shorter
blue-shifted
Since they are shorter, this means that they are blue shifted.
blue-shifted
receding side
From the receding side, however, the returning waves are longer.
longer
blue-shifted
red-shifted
And since they are longer, this means that they are red shifted.
blue-shifted
red-shifted
It’s the amount of red and blue shift…
blue-shifted
red-shifted
…which determines Mercury’s rate of rotation.
blue-shifted
red-shifted
The faster Mercury rotates on its axis…
blue-shifted
red-shifted
…the more red and blue shift will be observed.
blue-shifted
red-shifted
The slower Mercury rotates on its axis…
blue-shifted
red-shifted
…the less red and blue shiftwill be observed.
Mercury revolves the Sun in only 88 days.
Revolution
00.00Days
Mercury revolves the Sun in only 88 days.
Revolution
05.50Days
Mercury revolves the Sun in only 88 days.
Revolution
11.00Days
Mercury revolves the Sun in only 88 days.
Revolution
16.50Days
Mercury revolves the Sun in only 88 days.
Revolution
22.00Days
Mercury revolves the Sun in only 88 days.
Revolution
29.50Days
Mercury revolves the Sun in only 88 days.
Revolution
33.00Days
Mercury revolves the Sun in only 88 days.
Revolution
38.50Days
Mercury revolves the Sun in only 88 days.
Revolution
44.00Days
Mercury revolves the Sun in only 88 days.
Revolution
49.50Days
Mercury revolves the Sun in only 88 days.
Revolution
55.00Days
Mercury revolves the Sun in only 88 days.
Revolution
60.50Days
Mercury revolves the Sun in only 88 days.
Revolution
66.00Days
Mercury revolves the Sun in only 88 days.
Revolution
71.50Days
Mercury revolves the Sun in only 88 days.
Revolution
77.00Days
Mercury revolves the Sun in only 88 days.
Revolution
82.50Days
Mercury revolves the Sun in only 88 days.
DaysRevolution
88.00Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
00.00Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
07.38Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
14.75Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
22.12Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
29.50Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
36.88Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
44.25Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
51.63Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
59.00Days
Mercury rotates on its axis with a sidereal period of 59 days.
Sidereal Rotation
59.00Days pointing
upward
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
000.00Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
007.36Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
014.75Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
022.12Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
029.50Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
036.88Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
044.25Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
051.63Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
059.00Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
066.37Days
Synodic Rotation
073.74Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
081.11Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
088.00Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
095.36Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
102.24Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
111.12Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
118.00Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
123.63Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
131.25Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
138.90Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
146.50Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
154.12Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
161.75Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
169.38Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
176.00Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
Synodic Rotation
176.00Days
Mercury’s noon-to-noon, however, requires 176 days to complete.
noon
Notice the relationship between Mercury’s noon-to-noon and its year.
176 days = (88 days) x 2
Its noon-to-noonis exactly twice as long as its year.
Notice also that the 176-day synodic rotation…
176 days = (59 days) x 3
…is exactly equal to 3 sidereal rotations.
It’s merely a coincidence how these numbers relate to each other.
000.00Day Counter
0
00
Sidereal
Revolution
Synodic
007.38Day Counter
0
00
Sidereal
Revolution
Synodic
014.78Day Counter
0
00
Sidereal
Revolution
Synodic
022.15Day Counter
0
00
Sidereal
Revolution
Synodic
029.52Day Counter
0
00
Sidereal
Revolution
Synodic
036.89Day Counter
0
00
Sidereal
Revolution
Synodic
044.26Day Counter
0
00
Sidereal
Revolution
Synodic
051.63Day Counter
0
00
Sidereal
Revolution
Synodic
059.00Day Counter
0
00
Sidereal
Revolution
Synodic
059.00Day Counter
0
00
Sidereal
Revolution
Synodic
059.00Day Counter
0
10
Sidereal
Revolution
Synodic
059.00Day Counter
0
10
Sidereal
Revolution
Synodic
After 59 days in orbit,
059.00Day Counter
0
10
Sidereal
Revolution
Synodic
After 59 days in orbit, Mercury completes 1 sidereal day.
059.00Day Counter
0
10
Sidereal
Revolution
Synodic
066.37Day Counter
0
10
Sidereal
Revolution
Synodic
073.74Day Counter
0
10
Sidereal
Revolution
Synodic
081.11Day Counter
0
10
Sidereal
Revolution
Synodic
088.00Day Counter
0
10
Sidereal
Revolution
Synodic
088.00Day Counter
0
10
Sidereal
Revolution
Synodic
After 88 days in orbit,
088.00Day Counter
0
10
Sidereal
Revolution
Synodic
After 88 days in orbit, Mercury completes 1 revolution.
088.00Day Counter
0
10
Sidereal
Revolution
Synodic
After 88 days in orbit, Mercury completes 1 revolution.
088.00Day Counter
0
11
Sidereal
Revolution
Synodic
After 88 days in orbit, Mercury completes 1 revolution.
088.00Day Counter
0
11
Sidereal
Revolution
Synodic
096.36Day Counter
0
11
Sidereal
Revolution
Synodic
103.24Day Counter
0
11
Sidereal
Revolution
Synodic
111.12Day Counter
0
11
Sidereal
Revolution
Synodic
118.00Day Counter
0
11
Sidereal
Revolution
Synodic
118.00Day Counter
0
11
Sidereal
Revolution
Synodic
After 118 days in orbit,
118.00Day Counter
0
11
Sidereal
Revolution
Synodic
After 118 days in orbit, Mercury completes 2 sidereal days.
118.00Day Counter
0
11
Sidereal
Revolution
Synodic
After 118 days in orbit, Mercury completes 2 sidereal days.
118.00Day Counter
0
21
Sidereal
Revolution
Synodic
After 118 days in orbit, Mercury completes 2 sidereal days.
118.00Day Counter
0
21
Sidereal
Revolution
Synodic
123.63Day Counter
0
21
Sidereal
Revolution
Synodic
131.25Day Counter
0
21
Sidereal
Revolution
Synodic
138.90Day Counter
0
21
Sidereal
Revolution
Synodic
145.50Day Counter
0
21
Sidereal
Revolution
Synodic
154.12Day Counter
0
21
Sidereal
Revolution
Synodic
161.75Day Counter
0
21
Sidereal
Revolution
Synodic
169.38Day Counter
0
21
Sidereal
Revolution
Synodic
176.00Day Counter
0
21
Sidereal
Revolution
Synodic
176.00Day Counter
0
21
Sidereal
Revolution
Synodic
After 176 days in orbit,
176.00Day Counter
0
21
Sidereal
Revolution
Synodic
After 176 days in orbit, 3 things happen with Mercury.
176.00Day Counter
0
21
Sidereal
Revolution
Synodic
176.00Day Counter
0
21
Sidereal
Revolution
Synodic
Mercury achieves
176.00Day Counter
0
21
Sidereal
Revolution
Synodic
Mercury achieves its third sidereal day.
176.00Day Counter
0
21
Sidereal
Revolution
Synodic
Mercury achieves its third sidereal day.
176.00Day Counter
0
31
Sidereal
Revolution
Synodic
Mercury achieves its third sidereal day.
176.00Day Counter
0
31
Sidereal
Revolution
Synodic
176.00Day Counter
0
31
Sidereal
Revolution
Synodic
It also completes
176.00Day Counter
0
31
Sidereal
Revolution
Synodic
It also completes 2 revolutions around the Sun.
176.00Day Counter
0
31
Sidereal
Revolution
Synodic
It also completes 2 revolutions around the Sun.
176.00Day Counter
0
32
Sidereal
Revolution
Synodic
It also completes 2 revolutions around the Sun.
176.00Day Counter
0
32
Sidereal
Revolution
Synodic
176.00Day Counter
0
32
Sidereal
Revolution
Synodic
And at the same time,
176.00Day Counter
0
32
Sidereal
Revolution
Synodic
And at the same time, Mercury also completes 1 synodic
day.
176.00Day Counter
0
32
Sidereal
Revolution
Synodic
And at the same time, Mercury also completes 1 synodic
day.
176.00Day Counter
1
32
Sidereal
Revolution
Synodic
And at the same time, Mercury also completes 1 synodic
day.
176.00Day Counter
1
32
Sidereal
Revolution
Synodic
176.00Day Counter
1
32
Sidereal
Revolution
Synodic
Since the number “176”
176.00Day Counter
1
32
Sidereal
Revolution
Synodic
Since the number “176” is a multiple of both “88” and “59”…
176.00Day Counter
1
32
Sidereal
Revolution
Synodic
176.00Day Counter
1
32
Sidereal
Revolution
Synodic
…then all 3 of these numbers
176.00Day Counter
1
32
Sidereal
Revolution
Synodic
…then all 3 of these numbers changed on exactly the same day.
176.00Day Counter
1
32
Sidereal
Revolution
Synodic
…then all 3 of these numbers changed on exactly the same day.
Space Probes to Mercury
Mercury was visited by the Mariner 10 spacecraft in 1974.
Mariner 10 mapped Mercury’s surface, and took the first close-up photographs.
In 2004 NASA launched the Mercury
Messenger probe.
This was only the second probe ever sent to the planet Mercury.
In January, 2008 Messenger arrived at Mercury.
Messenger’s discoveries are yet to be revealed.
Mercury’s Interior
Mercury’s density is much higher than the Moon’s density.
This indicates that Mercury’s core has a high concentration of heavy
metals.
60% of Mercury’s total mass consists of an iron-nickel core.
iron-nickel core
iron-nickel corerocky crust
The surrounding crust consists of silicate rock.
iron-nickel corerocky crust
700 km
Mercury’s rocky crust is nearly 700 km thick.
This slide compares the cores of the Earth, Moon, and Mercury.
Notice that Mercury’s core is a ball of metal the size of the Moon.
A weak magnetic field has been detected around Mercury.
This indicates that some portion of the core is liquid.
History of Mercury
Dominated by ancient lava
flows and heavy meteorite
bombardment.
Radar image suggests icy
polar cap.
Mercury shows no evidence of plate tectonics or faulting.
However, its surface has long creases.
These creases formed from wrinkling caused when
Mercury cooled and shrank.
The Surface of Mercury
Very similar to Earth’s moon:
Heavily battered with craters, including some large basins.
Largest basin: Caloris Basin
Terrain on the opposite side jumbled by seismic waves
from the impact.
Lobate Scarps
Curved cliffs, probably formed when Mercury shrank while cooling down
The Plains of MercuryNo large maria, but intercrater plains:
Marked by smaller craters (< 15 km) and secondary impacts
Smooth plains:
Even younger than intercrater plains
Mercury VS
The Moon
The surface of Mercuryresembles the surface of the Moon.
Can you look at the 2 photos and tell which one is Mercury?
MoonMercury
Can you look at the 2 photos and tell which one is Mercury?
Both bodies are heavily cratered.
Moon Mercury
Both bodies are similar
in size and appearance.
Moon Mercury
And neither body has an atmosphere.
Moon Mercury
There are 2 reasons why Mercury has no atmosphere.
In the first place, the surface gravity on Mercury is too low.
With so little gravity, it is unable to retain an atmosphere.
Secondly, in being so close to the Sun…
…heated gases have the kinetic energy to escape Mercury and to fly off
into space.
Look closely at the 2 crescents.
Which side is Mercury, and which side is the Moon?
If this was your guess, then you were correct.
Mercury Moon
Here’s another one: Mercury or the Moon?
It’s Mercury, but it also looks like the lunar surface.
It’s Mercury, but it also looks like the lunar surface.
Mercury Moon
Surface Temperature
Mercury’s temperature range is the greatest of any planet.
Its daytime temperature can reach 700o Fahrenheit.
700o F
700o F -100o F
And its nighttime temperature can reach -100o Fahrenheit.
All planets without atmospheres get very cold at night.
700o F -100o F
But because Mercury is so close to the Sun…
700o F -100o F
…its daytime temperatures exceed those of all other planets.
700o F -100o F
700o F -100o F
+700o F – (-100o) = 800o F
So Mercury ranges nearly 800o F between daytime and nighttime.
Mercury Statistics
Mass (kg) 3.303e+23 Mass (Earth = 1) 5.5271e-02 Equatorial radius (km) 2,439.7 Equatorial radius (Earth = 1) 3.8252e-01 Mean density (gm/cm^3) 5.42 Mean distance from the Sun (km) 57,910,000 Mean distance from the Sun (Earth = 1) 0.3871 Rotational period (days) 58.6462 Orbital period (days) 87.969 Mean orbital velocity (km/sec) 47.88 Orbital eccentricity 0.2056 Tilt of axis (degrees) 0.00 Orbital inclination (degrees) 7.004 Equatorial surface gravity (m/sec^2) 2.78 Equatorial escape velocity (km/sec) 4.25 Visual geometric albedo 0.10 Magnitude (Vo) -1.9 Mean surface temperature 179°C Maximum surface temperature 427°C Minimum surface temperature -173°C Atmospheric composition Helium 42%Sodium 42%Oxygen 15%Other 1%
Mercury