From Cassini to Magellan: Unveiling the Topography of Venus

Venus, one of the brightest planets in the night sky, was observed by people throughout history. The planet was given various names by ancient astronomers. In this post I am sharing maps of Venus dated from the 1700s to the early 1990s.

Giovanni Domenico Cassini, an astronomer and topographer, observed the planets in our solar system from the mid 1600s until his death in 1712. He played a crucial role in the establishment of the Paris Observatory in 1671. Featured above is an illustration from an atlas that was published in 1754 by Nicolas de Fer. The illustration shows an image of Venus based on Cassini’s observations.

Below are maps of Venus, Jupiter and Mars, also based on observations by Cassini. The maps are from an atlas published by the British Cartographer and Hydrographer to the King, John Seller.

The transit of Venus occurs when the planet is positioned between the earth and the sun. During the transit, Venus appears as a tiny dot against the backdrop of the sun.  This event happens once every 243 years, with a pair of transits occurring eight years apart. The first recorded observation of the transit of Venus was made in 1639 by the British astronomers Jeremiah Horrocks and William Crabtree. The following diagram of the earth shows the transit of Venus as it happened in 1639.

During the 1800s and early 1900s astronomers developed various theories about the atmosphere and surface of Venus. Some scientists believed that the planet could support life. The diagrams featured below are from an early 20th century book that explores the possibility of life on Venus.

In 1961 scientists used Earth-based radar to observe Venus. Since that time successful missions to Venus have been carried out by the space programs of the United States, the Soviet Union, Japan, and the European Space Agency. The orbiter Magellan was launched by NASA in May 1989. The goal of the Magellan mission was to map the entire surface of Venus. The successful mission covered 98% of the planet’s surface. The mission lasted from May 4, 1989 to October 13, 1994 and consisted of six mapping cycles. The planning chart below was prepared for cycle three by Shannon McConnell, a scientist at NASA’s Jet Propulsion Lab.

Pictured below is an image of the transparent overlay that accompanies the chart.

The following topographic maps of Venus were published during the early 1990s by the United States Geological Survey. Radar imagery was used by scientists at U.S.G.S. to produce a series of  maps of Venus. Places named after the goddesses Ishtar, Aphrodite, and Lakshmi are shown on the maps. The mountain Maxwell Montes is also shown. Maxwell Montes was named after James Clerk Maxwell, a Scottish mathematical physicist.

Scientists have discovered that the average temperature of Venus is 867 degrees Fahrenheit, the surface is covered with volcanic landforms, and that water once existed on the planet. Learn more about Venus  by watching the following videos sponsored by the Science, Technology, and Business Division of the Library of Congress.

Discover More:

Venus: the Forgotten, Mysterious Planet by Dr. Lori Glaze, NASA.

The Transit of Venus by Dr. Sten Odenwald, NASA.