The Solar System:


“La nascita di Venere” (“The Birth of Venus”) by Sandro Botticelli (c. 1445-1510 CE; Italian), c. 1484–86 CE.

Credit: Sandro Botticelli; Uffizi Gallery; Google Art Project [link]

Venus transit 2012

On 5 June 2012, the satellite Hinode captured this stunning view of the transit of Venus across the Sun -- the last instance of this rare phenomenon visible from Earth until 2117. Hinode is a joint JAXA/NASA mission to study the Sun's surface magnetism, primarily in and around sunspots.

Credit: JAXA/NASA/Lockheed Martin [link]

Visible Venus

When Japan’s Akatsuki spacecraft closed in on Venus in late 2010 after a 6 month trip from Earth, its main engine failed. With no way of slowing down, the spacecraft overshot Venus and barreled into orbit around the Sun.

The mission, meant to study the dynamics of the planet’s perpetual cloud cover and hellishly hot surface, was feared lost. But failed engine aside, the spacecraft was in good working order. So five years later, when its orbital path neared Venus, engineers used a separate set of thrusters intended for attitude control to slow Akatsuki into an elliptical orbit around the planet. The spacecraft then began its delayed mission of photographing Venus in ultraviolet and infrared light, revealing unprecedented details of the dynamic weather patterns on Venus.

Photographed in ultraviolet light and rendered in false color, this Akatsuki image of Venus reveals the complexities of the clouds that coat the planet. The ocher hues correspond to sulfur dioxide. The thick, cloudy atmosphere of Venus completely obscures any glimpse of the planet's surface.

Credit: JAXA/ISIS/DARTS/Damia Bouic [link]

Invisible Venus

By using radar techniques to penetrate the thick global cloud cover of Venus, we can construct a detailed map of the planet's surface. Information about the elevation and roughness of the terrain can be obtained.

These global views of the surface of Venus were made from Magellan space probe synthetic aperture radar mosaics. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft.

Credit: NASA/JPL [link]
Credit: NASA/JPL [link]

On the surface of Venus

The Soviet (Russian) space probe Venera 13 landed on Venus on 1 March 1982. The lander functioned for at least 127 minutes (the planned design life was 32 minutes) in an environment with a temperature of 457 °C (855 °F) and a pressure of about 90 Earth atmospheres. The descent vehicle transmitted data to the satellite, which acted as a data relay as it flew by Venus. This Venera 13 surface images have been corrected for the spherical panorama view of the camera. The upper photo shows the image as seen on Venus. The rocks are a dull gray, but sunlight filtered by the thick atmosphere gives them a yellow tint. The lower photo has been corrected to show the color of the surface as it would appear under direct sunlight (i.e., as if viewed on Earth). The flate plates of rock are thought to be basalt, with dark soil between some of them. This site is probably typical of the plains on Venus.

Credit: Russian Academy of Sciences; reprocessing of original data by Don P. Mitchell [link]

Views of the Venusian surface from the Soviet (Russian) Venera landers. Clockwise from the top: Venera 10, Venera 14, Venera 9, and Venera 13. These images show somewhat different landscape features in four different areas on Venus.

Credit: Russian Academy of Sciences; reprocessing of original data by Ted Stryk [link]

Backwards or upside-down?

Very slow rotation

  • A Venus day (243 Earth days) is longer than a Venus year (225 Earth days).

  • Slow rotation = very weak (virtually nonexistent?) magnetic field.

Retrograde rotation

  • Almost all planets (like Earth) rotate in the same direction they orbit the Sun.

  • This is the most likely result from conservation of angular momentum during the formation of the solar system.

  • But Venus rotates in the opposite direction from its orbit.

  • On Venus, the Sun rises in the west and sets in the east.


Possibly a giant collision with a planet sized object that either reversed the direction of rotation, or flipped Venus on its axis?

Rotation axis tilts of the planets. The terrestrial and giant planets are to scale within each group, but the groups are not in scale with each other. Axis tilt data from the Planetary Fact Sheet at the NASA Space Science Data Coordinated Archive.

Credit: D. W. Hoard (2018), assembled from public domain images by NASA

Hottest planet in the Solar System

(even hotter than Mercury)

  • Average surface temperature = 735 K (462 °C; 863 °F) -- lead melts at "only" 327 °C

  • Surface atmospheric pressure = about 90-93x Earth

  • Atmospheric composition =

      • 96.5% carbon dioxide

      • 3.5% nitrogen

      • traces of other gases (e.g., sulfur dioxide)

      • no oxygen (no plant life to release free oxygen into atmosphere!)

      • no water (floated to top of dense atmosphere; split into H and O by UV light from the Sun; blown away by solar wind)

Why is Venus so hot?

The Runaway Greenhouse Effect

Panorama images from both cameras on the Venera 13 probe reprocessed into perspective images of the surface of Venus.

Credit: Russian Academy of Sciences; reprocessing of original data by Don P. Mitchell [link]

Metal snow!

Metallic minerals, such as bismuth sulfide (bismuthinite) and lead sulfide (galena), melt and evaporate at low altitudes on the hot surface of Venus.

The metal vapor circulates upward in the atmosphere and precipitates onto the surface as “snow” at higher (colder) altitudes.

It can be detected as a bright reflected signal in radar maps of mountains on Venus.

Radar map of Maxwell Montes, the highest mountain on Venus, from the Magellan space probe. The mountain rises almost 11 km (6.8 miles) above the mean planetary radius. The western slopes descending to Lakshmi Planum (on the left) are very steep, whereas the eastern slopes descend gradually into Fortuna Tessera. The broad ridges and valleys making up Maxwell and Fortuna suggest that the topography resulted from compression of the surface. The near-vertical black lines are gaps in the radar mapping of the surface.

The prominent circular feature on the eastern slope of Maxwell is Cleopatra. Cleopatra is a double-ring impact basin about 100 km (62 miles) in diameter and 2.5 km (1.5 miles) deep. A steep-walled, winding channel a few kilometers wide breaks through the rough terrain surrounding the crater rim. A large amount of lava originating in Cleopatra flowed through this channel and filled valleys in Fortuna Tessera. Cleopatra is superimposed on the structures of Maxwell Montes and appears to be undeformed, indicating that Cleopatra is relatively young.

Credit: NASA/JPL [link]

In this expanded view of the area around Cleopatra on Maxwell Montes, a steep-walled, winding channel a few kilometers wide can be seen to break through the rough terrain surrounding the rim of the impact basin (upper right of crater edge). A large amount of lava originating in Cleopatra flowed through this channel and filled valleys in Fortuna Tessera.

Credit: NASA/JPL [link]

A young surface

  • The surface of Venus displays relatively few impact craters with little erosion, indicating they are all young.

  • Venus appears to have been completely resurfaced about 750 Myr ago.

  • There is currently no tectonic activity on Venus, but there are numerous large volcanos (including some that are possibly still active).

  • It is possible that these volcanos produce a joint mega-eruption that covers the entire planetary surface with fresh lava every few hundred million years.

The volcanic peak Idunn Mons (at 46 degrees south latitude, 214.5 degrees east longitude) in the Imdr Regio area of Venus. This image combines topographic and radar data from NASA's Magellan space probe. The topography has been vertically exaggerated by 30 times. Bright areas are rough or have steep slopes. Dark areas are smooth. Idunn Mons has a diameter of about 200 kilometers (120 miles), and a peak height of about 2.5 km (1.6 miles) above the surrounding plains.

Credit (image and some text): NASA/JPL-Caltech/ESA [link]

The colored overlay on the Magellan map of Idunn Mons shows the heat patterns derived from surface brightness data collected by the European Space Agency's Venus Express spacecraft. Red-orange is the warmest area and purple is the coolest. The warmest area is centered on the summit and the bright flows that originate there, indicating the Idunn Mons might still be an active volcano.

Credit (image and some text): NASA/JPL-Caltech/ESA [link]

Exploring the surface of Venus

Model of the identical Venera 13 and 14 probes that landed on Venus.

Credit: Hopea114y (Wikimedia Commons), CC BY SA 4.0 [link]

A NASA Venus rover concept utilizing a Stirling cooler to refrigerate internal electronics that are contained in a pressure-resistant housing. A Stirling cooler uses the compression and expansion of gas in a piston to transfer heat from "inside" to "outside". The electronics inside the rover would operate at 200 °C and the external radiator at 500 °C. Since the Venusian atmosphere is "only" 450 °C, the radiator would dissipate heat from the rover. This rover would require a radioisotope (nuclear) generator to provide its electrical power.

Credit: NASA/Glenn Research Center [link]

Concept for the AREE (Automaton Rover for Extreme Environments) mechanical rover for exploring Venus. The rover features:

    • Mechanical computers; minimal reliance on electronics.

    • Symmetric tank tread design that allows operation even if the rover flips over (e.g., from strong winds or steep terrain)

    • Powered by a central wind turbine with backup solar panels.

    • Energy is stored in springs.

    • Mechanical communications system using rotating radar targets that are "read" by an orbiting satellite.

Credit: NASA/JPL-Caltech [link]

Sending humans to Venus?

At an altitude of 55 km in the atmosphere of Venus:

  • Temperature = 300 K = 27 oC = 81 oF

  • Pressure = 50% Earth surface

    • Equivalent to pressure at an altitude of about 5,500 m (18,000 ft) on Earth

  • Gravity = 90% Earth surface

  • Higher atmosphere layers offer protection from the Sun's UV light and solar wind.

  • The atmosphere is still slightly acidic, but nothing a hazmat suit can’t handle.

Conditions high in the atmosphere of Venus offer less obstacles to human habitability than the surface of Mars!

Atmospheric profile of Venus. The left vertical axis indicates altitude (in km) above the surface of Venus, while the right vertical axis indicates atmospheric pressure (1 bar corresponds to slightly less than Earth atmospheric pressure at sea level). The horizontal axis is temperature (in K); the corresponding temperature as a function of altitude and pressure in the atmosphere is indicated by the blue line.

Credit: © 2001 Pearson Education, Inc. [link]

NASA mission concept for a crewed floating outpost (a "cloud city") on Venus, called the High Altitude Venus Operational Concept (HAVOC).

Credit: NASA [link]