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Discover the fascinating features of Venus, a hot and geologically active planet with dense atmosphere and volcanic landscapes. Learn about its unique characteristics, surface temperature, and past exploration missions.
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Summary: Mercury is a small, hot, dry, airless, geologically dead world whose surface resembles the Moon. It is heavily cratered. It has the greatest day-night temperature range of any planet or moon. It has the greatest density of any planet or moon because of its massive metal core. The single most visible feature is Caloris Basin. It’s surface displays “wrinkles” known as scarps. It possesses a weak magnetic field.
Astronomy 04 The Solar System Chapter 10: "Earthlike Planets - Venus & Mars”
Venus approaches nearer Earth than any planet. At inferior conjunction, Venus can come within about 42 million kilometers or 25 million miles of Earth. Venus is brighter in our skies than any other planet. Venus brightness is a result of its nearness and its highly reflective white cloud cover. Venus can cast a shadow!
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Venus orbits the Sun in the least eccentric (most circular) of all planetary orbits. Venus revolves about the Sun once in 225 days but takes 243 days to complete a single rotation Venus has the unique distinction of having its day longer than its year! Venus direction of rotation is retrograde – opposite the direction of rotation of most of the other planets.
Venus has a very dense atmosphere - perhaps a 100 times thicker than Earth’s. The atmosphere is composed of • 97% Carbon Dioxide • 2% Nitrogen • 1% of Oxygen, Water Vapor and Methane
The thick white clouds that cover Venus are composed of Sulfuric Acid. The clouds are also very high. The bottoms of the clouds on Venus are higher than the tops of the very highest clouds on Earth.
Venus has the highest surface temperature of any planet – about 900F. The planet’s high surface temperature is a result of a “runaway greenhouse effect.” Carbon dioxide in the atmosphere traps the Sun’s heat. Unlike Mercury which has a large diurnal temperature range, temperatures on Venus are relatively uniform everywhere on the planet’s surface.
More spacecraft have been sent to Venus than any other planet. The Russian Venera 7 was first spacecraft to land on Venus and broadcast data form its surface in 1970.
The U.S. Pioneer 12 spacecraft was the first to generate a crude radar map of the planet’s surface.
The U.S. Magellan spacecraft mapped Venus in great detail using advanced radar imaging between 1991 and 1993. The Magellan spacecraft returned more data to Earth than all previous missions to Venus combined.
Magellan Spacecraft Image of Venus The effective resolution of this image is about 3 kilometers. It was processed to improve contrast and to emphasize small features, and was color-coded to represent elevation.
Venus Radar Map generated by the Magellan Spacecraft Test 3 will be on Mon 3/17. Review will be Fri 3/14
The Surface of Venus: There is no evidence of plate tectonics on Venus. 75% of the surface is covered by lowland lava plains similar to the basaltic ocean basins of Earth. These plains were formed in much the same way the maria were formed on the Moon. Rising above the lava plains are two “continents”: • Aphrodite Terra – about the size of Africa • Ishtar Terra – about the size of Australia
The Surface of Venus: Ishtar Terra contains the highest region on Venus – the Maxwell Mountains which rise 11 km (36,000 ft) above the surrounding lowlands. The dense atmosphere of Venus did protect the planet from smaller planetesimal impacts (less than 10 km). A count of the larger craters indicate an age for the current surface of Venus at 500-600 million years. Next to Earth Venus is the most geologically active terrestrial planet.
The Surface of Venus: Venus has experienced widespread volcanism. It’s present surface was probably formed in some sort of planet-wide volcanic convulsion 500 million years ago. The largest volcano on Venus is Sif Mons – 500 km across and 3 km high. Thousands of smaller volcanoes are scattered across the planet’s surface. Unusual volcanoes called “pancake domes” (25 km in diameter and 2 km high) were formed from very thick, viscous lava.
Craters - Venus is scarred by numerous impact craters distributed randomly over its surface. Small craters less that 2 kilometers are almost non-existent due to the heavy Venusian atmosphere. Note the lava flows around the rims.
Volcanoes - Volcanic features are common on Venus. 85% of the Venusian surface is covered with volcanic rock. Hugh lava flows have flooded the lowlands creating vast plains. More than 100,000 small shield volcanoes dot the surface along with hundreds of large volcanos. Flows from volcanos have produced long sinuous channels extending for hundreds of kilometers, with one extending nearly 7,000 kilometers.
Fault lines - In images of the Alpha Regio, bright terrain is shown to be a series of troughs, ridges, and faults that are oriented in many directions. The lengths of these features generally range from 10 kilometers to 50 kilometers.
Arachnoids - Arachnoids are oval features with concentric rings and a complex network of fractures extending outward. The arachnoids range in size from approximately 50 kilometers to 230 kilometers in diameter. They might have resulted from an upwelling of magma from the interior of the planet which pushed up the surface to form "cracks".
The Surface of Venus: Another interesting feature are coronae – bulges in the crust where hot magma is rising from below. One of the most famous is Fotla Corona a circular feature that bears a striking resemblance to a Muppets character.
Astronomy 04 The Solar System Chapter 22: “Our Neighbors - Venus & Mars” Test 3 on Mon 6/16. Review on Fri 6/13.
Summary: Venus is Earth “sister” in size. Venus comes closer to Earth and is brighter than any planet. Venus day is longer than its year. Venus has the thickest atmosphere of the terrestrial planets. Venus is cover by an unbroken layer of sulfuric acid clouds. Venus atmosphere is almost all carbon dioxide. Venus is the hottest of all planets. Venus is “geologically alive” – like Earth. Venus surface has lowland lava plains, continents, mountains and craters.
Mars due to its distinctly red coloration was named after the Roman god of war. Mars orbits the Sun at an average distance of 227 million km or 141 million miles. It’s orbit is considerably more eccentric than Earth’s with a variation of 42 million km (26 million miles). Mars day is about 24 hour 37 minutes long and it’s rotational axis is tiled at about 25 degrees. Mars can approach within 35 million miles of Earth.
The best Earth-based telescopic views reveal the polar caps and light and dark colored regions.
Mars small size and mass (0.11 X Earth) enables it to retain only a thin atmosphere. (1% that of Earth). Mars atmosphere is 95% carbon dioxide, 3% nitrogen and 2% argon. Water ice clouds frequently form in the Martian atmosphere. No liquid water exists on Mars because of the low atmospheric pressure. Although the atmosphere is thin strong winds do develop in the Martian atmosphere. These winds create huge sand storms.
In 1877 Giovanni Schiaperelli observed what he called “canale” or channels on Mars. In English-speaking countries the term was mistakenly translated as “canals” implying artificial origin. American astronomer Percival Lowell believed the Schiaparelli’s “canals” were the work of intelligent Martians.
American astronomer Percival Lowell believed the Schiaparelli’s “canals” were the work of intelligent Martians. This is his map of Mars’ canals.
Spacecraft Exploration of Mars: The U.S. Mariner 4 spacecraft flew by Mars in 1965 revealing what appeared to be a “moon-like world.
Mariner 9 orbited Mars in 1971 and mapped the entire surface of the planet.
The Viking 1 and 2 spacecraft landed on Mars in 1976 and performed a series of experiments in search of simple life. The results were negative.
The Surface of Mars: Like the Earth, Moon and Venus the surface of Mars has continental or highland areas as well as lower volcanic plains. The 10-km high Tharsis Bulge is a continental area the size of North America. Four great volcanoes rise another 15 km above this region. The greatest volcano is Olympus Mons with a diameter of 500 km and a height of 25 km.
Olympus Mons – The largest volcano (extinct) in the Solar System.
