Start Here!

Please testimonial the properties of the inner Planets at bill Arnett"s nine 8 Planets website, great resource.

You are watching: Which planet is the most heavily cratered of the terrestrial planets

Additionally, there is a an excellent deal of information (with no stroked nerves ads, like in the previous link) at NASA"s Solar System exploration page.

Our goal because that this class is to come up v a perform of the similarities in between the planets, some patterns in your properties, and also an knowledge of where few of the imbalances in your properties might lie. To achieve this, we can begin with a an easy bullet perform that has a review of the nature of every of the three Terrestrial planets:



Surface greatly cratered—in some methods very similar to Earth"s Moon.Very dark—only shows a small amount of sunlight (it has a short albedo).Temperature on the surface varies indigenous 100K to nearly 700K.In a 3:2 synchronous orbit through the Sun—three Mercury work (59 planet days each) = 2 Mercury year (88 earth days each).The iron core of Mercury is really large, taking up many of the inner of the planet and also creating a fairly strong magnetic ar for a planet of that is size.No moon.Less 보다 the size of the Earth.Messenger rather surprisingly revealed that Mercury has actually water ice in shadow in craters in ~ its poles!

Figure 11.9: Venus
Credit: NASA Magellan Mission


Thick atmosphere and "runaway greenhouse effect" causes 730K surface ar temperatures.Atmosphere is composed mostly of CO2 (carbon dioxide), clouds of sulfuric acid—no water vapor or oxygen.Huge volcanoes.Clouds are very reflective (high albedo)—Venus is among the brightest objects in our night sky.Rotates very slowly (243 earth days) and it rotates in a retrograde manner (opposite that the earth & Sun).Not in a synchronous orbit—one Venus year = 225 planet days.No moon.Almost identical in dimension to the Earth.A variety of missions come Venus have actually been sent out by the USA and also USSR. In 1994, Magellan mapped the surface ar of Venus.

Figure 11.10: Mars
Credit: space Telescope science Institute


Temperature always below the freezing point of water.Giant volcanoes (largest of any in the whole Solar System).Intense, large dust storms.Has an setting that is much thinner than planet or Venus, mainly CO2.The surface is red because of the visibility of iron oxide (rust).One Mars job is just slightly longer than an earth day (24.6 hours).One Mars year is 1.88 earth years.Polar cap of dry ice and water ice cream that readjust with the seasons.Frozen water in a permafrost layer (recently confirmed).About fifty percent the dimension of Earth.Two small, irregularly shame moons—Phobos and also Deimos.The many visited world in ours Solar System, consisting of several current missions, Mars exploration Rovers Spirit and Opportunity, the Phoenix Lander, Curiosity, and MAVEN.

Interior structure

There are number of peculiarities around these planets, however we can understand the likely causes of these properties as soon as we comparison them to the Earth. First, think about the internal structure of these planets. Similar to the Earth, Mercury, Venus, and also Mars space differentiated. Curiously, we uncover that, compared to the various other planets, Mercury"s main point is relatively large. The is, it filling up many of the internal of this planet. Due to the fact that the main point of Mercury is probably mostly comprised of iron and nickel and also it fills so lot of the planet"s interior, Mercury is the densest within planet. We intend that several of the core of each of the inner planets is molten, and we mean that this fluid metallic core have to generate electrical currents inside the world as the core rotates with the rest of the planet. These electric currents should develop magnetic fields, making the planets behave as if castle have giant bar magnets inside them. Both Mercury and the earth have measurable magnetic fields, but, contradictory to ours expectations, Venus and Mars carry out not. Because that Venus, the reason may be that it rotates too gradually to produce the necessary conditions to produce a magnetic field. The absence of magnetic ar on Mars might be led to by its lack of a molten core.


We watch the inner planets easily because they are adjacent and bright by showing sunlight. You have the right to see Mercury, Venus, and also Mars at different times the the year without any type of instruments favor a telescope or binoculars—all three of this planets space visible to your naked eye. Although every one of the planets reflect sunlight, various materials reflect different amounts of sunlight. Because that example, look at the planet at the NASA: The Blue Marble site. We check out that the brightest components of the earth are the clouds and the ice close to the phibìc Pole. The darkest parts of the globe are the spot of deep s that space not extended by clouds. The quantity of irradiate reflected by a surface is referred to as the albedo. For light fancy clouds, the albedo is high, and also much of the incoming sunshine gets reflected. Water and dark colored rock reflect much much less light. Mercury is mostly covered through dark rock, for this reason its albedo is very low. On the various other hand, Venus is spanned by a thick layer the clouds, for this reason it reflects almost all of the sunshine that hits it. Since of Venus" high albedo and also its proximity to the Earth, that is the brightest object in the night skies after the Sun and the Moon.


Observations of these planets tell us that all three have atmospheres. Mercury has a really thin setting with a weird composition. Mercury is so small that gas quickly escapes native its gravitational pull, for this reason its environment must it is in regenerated continually, maybe by the bombardment of the surface ar of the planet by energetic particles from the Sun. Venus, ~ above the various other hand, has a thick, thick atmosphere. The greenhouse result has "run away" top top Venus, do the surface temperature hotter 보다 Mercury, also though that is farther indigenous the Sun. Mars" atmosphere is lot thinner 보다 Venus or Earth, and it is composed primarily that carbon dioxide. The atmosphere of every inner earth originated as soon as the planet was formed and has been supplemented through gas that has escaped from underneath the crust.

The regulations of physics tell us that the hot a gas is, the quicker the particles inside that gas move. Because that Mercury and Mars, this planets are so little that they have weak gravitational fields, which method that lot of the gas in their setting can escape if that is warm enough (the median speed of the particles in the gas above the escape velocity from the planet). For Venus and the Earth, i beg your pardon are an ext massive and also have stronger gravitational fields, the lightest gases deserve to escape, but gases choose carbon dioxide and nitrogen do not.

Additionally, top top the Earth, we know that plant and also animal life process the gas in the atmosphere. For example, human beings breathe oxygen and exhale carbon dioxide, if plants use carbon dioxide and also produce oxygen. Since of these organic processes ~ above the Earth, our environment has evolved considerably from its original content. The Earth"s setting may have actually once been much like Venus" environment is now, however, as plant life on the planet arose, the process of photosynthesis contributed to the remove of carbon dioxide and the increase in oxygen content.

See more: Can You Eat Eggs On Fridays During Lent, What Can You Eat During Lent

Rates the rotation

There is also some diversity in the rotation prices of the inner planets. We room most familiar with the Earth. The rotates in a counterclockwise direction in close to 24 hours. Mars is quite similar to the Earth. That is rotation axis is tilted by 24 levels (Earth"s axial tilt is 23.5 degrees), and its rotation period is simply over 24 hours. So on Mars, the size of the day and also the sport in the height of the Sun over the horizon end the food of one Mars year are similar to what us are offered to ~ above the Earth. Mercury has end up being tidally locked to the Sun, similar to exactly how the Moon is locked to the Earth. However, in the instance of Mercury, the planet rotates in 59 days and orbits the sun in 88 days. What this method is that Mercury rotates totally on its axis (that is, 360 degrees) 3 times in the exact same amount of time the takes to orbit the sun 2 times. This is referred to as a 3:2 resonance. In the situation of the Moon, since it orbits the planet 1 time in the same amount that time as it rotates 1 time, this is referred to as a 1:1 resonance. Although this seems a little bit peculiar, Venus" rotation properties are lot stranger. The takes 243 days to rotate once (and there is no tidal locking, so the Venus year has actually nothing to perform with the Venus day), but it rotates in the contrary sense contrasted to Mercury, Earth, and also Mars. Every one of these planets orbit the sunlight in a counterclockwise direction, and also Mercury, Earth, and Mars revolve counterclockwise approximately their axes. Venus rotates gradually in a clockwise manner roughly its axis. One concept is that a collision or collisions with Venus by other objects caused its rotation sense to reverse, yet an alternate theory is that the tidal influence of the Sun and also the other planets in the Solar mechanism may also have caused this distinct rotation.