Lecture 19 - Venus & Mars (11/19/98)

Moon & Mercury --- | --- Outer Planets

Reading:

Chapter 5 (ZG4)

	Key Question:	What is the surface of Venus like, and how do we find out?
	Key Principle:	Geologic activity
	Key Problem:	What is the smallest scale feature we could see on Mars from the Earth?
	Key Quote:	"Venus and Mars are alright tonight ..." - Wings over America

Investigations:

1. Venus
   • How does Venus compare to the Earth in mass, radius, and density?
   • How much of the energy must be trapped for the surface of Venus to be 730K?
   • What happens to water above 600K?
   • What produced Venus's carbon dioxide atmosphere of 90 bars?
   • What are the cloud decks of Venus composed of?
   • How fast do Venus's cloud patterns rotate?
   • Why does Venus have a single convection cell per hemisphere, while the Earth has around three?
   • How fast does Venus's surface rotate? Which direction?
   • How long is a Venusian "day"?
   • How did the Magellan orbiter map the surface of Venus?
   • What surface features did it find?
   • Is Venus currently volcanically and/or geologically active?
   • Why does Venus have a substantial molten iron/nickel core, yet little or no magnetic field?
2. Mars - Physical Properties
   • In what ways is Mars most like the Earth in surface conditions of all the other planets?
   • Is it expected that Mars has much ongoing geologic activity?
   • How long is the Martian day? Year?
   • What is the mean density of Mars? What is the internal composition?
   • What is the surface gravity of Mars, compared to the Earth?

Exploring Venus:

Magellan global composite radar image of Venus (from the Jet Propulsion Lab Public Information Archive)

From Earth, it is clear that Venus is a cloud-shrouded world, and it was once thought that lush jungles could be hidden beneath the clouds!. However, the Soviet Venera landers showed us a scorched desert buried under more than 90 atmospheres of pressure with temperatures above 475 C!

For more information on Venus:

• The Venus Planet Profile in the JPL archives.
• Venus from Views of the Solar System, by Calvin J. Hamilton.
• Venus from The Nine Planets, by Bill Arnett.

Views of Mars:

(from the Jet Propulsion Lab Images and Video Archive)

The first Mariner images of Mars dispelled the notion of a world with canals and gardens. The cratered surface of Mars was photographed by Mariner 6's wide angle TV camera on July 30, 1969 at a range of 3,459 kilometers (2,150 miles). The area measures 901 kilometers (560 miles) by 692 kilometers (430 miles) and is located southeast of Meridiani Sinus about 15 degrees below the equator. The large crater at right is about 257 kilometers (160 miles) in diameter.

The Viking lander took images of Mars in 1976. These show the reddish hue of the Martian sky. The red cast is probably due to light scattered and reflected from sediment suspended in the lower atmsophere.

For more information on Mars and its moons:

• The Mars Planet Profile in the JPL archives.
• Mars from Views of the Solar System, by Calvin J. Hamilton.
• Mars from The Nine Planets, by Bill Arnett.

HST Captures Sharpest Earth-based pictures of Mars

Mars, courtesy STSCI

The Hubble Space telescope has taken a series of spectacular images of Mars. See the NASA press release for more details. Also see the CNN story on the Mars HST images (CNN 5/21/97).

• Latest HST Mars images and press release (STSCI 5/20/97)
• Earlier HST Mars images (STSCI 3/20/97)

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smyers@nrao.edu Steven T. Myers