Among the terrestrial planets, Earth and Venus have experienced the most geological activity over their histories, although some of the moons in the outer solar system are also surprisingly active.
In contrast, our own Moon is a dead world where geological activity ceased billions of years ago. Geological activity on a planet is the result of a hot interior. The forces of volcanism and mountain building are driven by heat escaping from the interiors of planets. As we will see, each of the planets was heated at the time of its birth, and this primordial heat initially powered extensive volcanic activity, even on our Moon.
But, small objects such as the Moon soon cooled off. The larger the planet or moon, the longer it retains its internal heat, and therefore the more we expect to see surface evidence of continuing geological activity. The effect is similar to our own experience with a hot baked potato: the larger the potato, the more slowly it cools.
If we want a potato to cool quickly, we cut it into small pieces. For the most part, the history of volcanic activity on the terrestrial planets conforms to the predictions of this simple theory. The Moon, the smallest of these objects, is a geologically dead world. Although we know less about Mercury, it seems likely that this planet, too, ceased most volcanic activity about the same time the Moon did. Mars represents an intermediate case. It has been much more active than the Moon, but less so than Earth.
Earth and Venus, the largest terrestrial planets, still have molten interiors even today, some 4. The giant planets have dense cores roughly 10 times the mass of Earth, surrounded by layers of hydrogen and helium. The terrestrial planets consist mostly of rocks and metals. They were once molten, which allowed their structures to differentiate that is, their denser materials sank to the center. The Moon resembles the terrestrial planets in composition, but most of the other moons—which orbit the giant planets—have larger quantities of frozen ice within them.
In general, worlds closer to the Sun have higher surface temperatures. The surfaces of terrestrial planets have been modified by impacts from space and by varying degrees of geological activity. Skip to main content. Search for:. Key Concepts and Summary The giant planets have dense cores roughly 10 times the mass of Earth, surrounded by layers of hydrogen and helium. They also design, install and test systems for space-bound equipment and ships.
Many other types of engineers — mechanical, electrical, computer, structural, chemical — design and create rockets, fuels, lenses, sensors, robotics, antennas, communication devices and computer programs that help humans explore space.
Students can explore orbit transfers and, specifically, Hohmann transfers with the associated activity A Roundabout Way to Mars by learning about the planets' orbits around the Sun, and about a transfer orbit from one planet to the other. After a soil-brushing experiment, the Mars Exploration Rover Spirit took this photo that shows iron oxide dust on the rock abrasion tool at the end of its robotic arm. Mars is the fourth planet from the Sun. It is known as the "red planet" because of its red appearance.
Mars has been visited many times by unmanned spacecraft. The first satellite, Mariner 4, reached Mars in The Viking Landers landed on the surface in More recently, the Spirit and Opportunity surface rovers landed in to spend years exploring the terrain, gathering samples and conducting experiments on the soil. Refer to the associated activity Are We Alone?
Why so much interest about Mars? Other than Earth, it has been identified as the most habitable planet for humans. There are also indications that Mars once held life, which could help us better understand the origins of life on Earth as well as other on planets that we do not even know about yet.
Mars is a rocky, dusty and dry planet with red soil contains iron oxide — rust. Like Earth, the terrain is varied with frozen polar caps that contain carbon dioxide on the South Pole and water-ice mixtures on the North Pole.
Mars also has one of the largest volcanoes in the solar system, Olympus Mons. It stands at about 27 km high. For comparison, the highest mountain on Earth Mt.
Everest is 8. Mars also contains a canyon system named Valles Marineris. The temperature varies from day to night and is very erratic, reaching o F at night and getting up to 1 o F during the day. Mars is not a warm place! Mars has two moons, Phobos fear and Deimos panic , named for the horses that pulled the chariot of the Greek god Ares.
Mars also has seasons. The summer temperature barely reaches above freezing and the rest of the year remains very cold and frozen with dust storms. At the North Pole is evidence of seasonal coverings of carbon dioxide on top of the water. Once, we thought there were canals on Mars, but there is not enough water left on Mars to account for the vast network of canals.
The poles also have alternating dust and ice. It is speculated that the layers may be evidence of unobserved seasonal changes. Further evidence of more water on Mars is the crater impacts that show outward marks that resemble the patterns of mud being hit.
It is the belief of scientists that the outermost moons the ones outside of Callisto's orbit are asteroids captured by the gravity of Jupiter. Unlike most of the other planets in our solar system, Jupiter is a gas giant made of mostly hydrogen and helium mixed with other trace elements.
These gases cause the brilliant color bands on the planet. If a probe were sent through Jupiter, it would find no solid surfaces, and as it traveled further through Jupiter, the gaseous material would become denser. Jupiter has a simple ring system and a huge magnetic field. Near Jupiter are many radioactive particles that make up radioactive belts.
The outer magnetosphere extends out 20 times the diameter of Jupiter. Jupiter has winds that reach an excess of km per hour and cause swirling patterns of clouds that change positions quickly in as little as a few hours.
Like other planets, Jupiter has distinguishing features. Its main one is a complex storm known as the Giant Red Spot that is about the size of the entire surface area of Earth! It rotates in a continuous counter-clockwise direction. The Red Spot is made from phosphorus, which condenses five miles above surrounding clouds. This altitude is cool enough to create the red color we see.
Table 1. Facts about Mars and Jupiter. Watch this activity on YouTube. Where do Mars and Jupiter fall in the order of planets from the Sun? Answer: Mars is the fourth planet from the Sun, and Jupiter is the fifth planet from the Sun. What are some of the characteristics of Mars and Jupiter?
Possible answers: Mars is called the "red planet," is the planet that is the most like the Earth, and has seasons like Earth, but the seasons go from very cold to even colder. Saturn's moon Titan has an atmosphere that extends farther above its surface than Earth's atmosphere. Uranus' Miranda has canyons deeper than the Grand Canyon and Neptune's Triton spews liquid nitrogen and methane from ice volcanoes. The exquisite banded rings circling Saturn make it one of the most recognizable of the larger planets.
However, all the larger planets have ring systems though less spectacular than Saturn's. David Chandler has been a freelance writer since whose work has appeared in various print and online publications. A former reconnaissance Marine, he is an active hiker, diver, kayaker, sailor and angler. He has traveled extensively and holds a bachelor's degree from the University of South Florida where he was educated in international studies and microbiology. What Are the Characteristics of the Planet Jupiter?
Facts About Neptune for a School Project. Saturn has 62 moons as of It is named for the Roman god of agriculture. Uranus is 51, kilometers in diameter, about 4. It revolves around the Sun slowly, taking 84 years to complete one orbit. It rotates in about 17 hours. It is covered by a thick layer of gas, and has a fairly uniform blue-green color.
Uranus has 27 moons as of and is surrounded by a system of nine rings. It is named for another Roman god, the grandfather of Jupiter. Neptune is slightly smaller than Uranus, with a diameter of 49, kilometers. It circles the Sun once every years, and rotates in 16 hours. Its atmosphere appears blue , and is marked by large dark blue storm systems. It is surrounded by a system of five rings and at least 14 moons. Neptune is named for the Roman god of the ocean. Pluto in was renamed as a dwarf planet.
It has an eccentric, oval-shaped orbit, which is tilted with respect to the rest of the Solar System. Pluto revolves around the Sun in years, and rotates in a period of 6. Pluto is probably composed of rock. Its surface and color are unknown. It has one large moon that is almost like a twin with 2 smaller moons.
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