Venus is the Earth-that-could-have-been and the Earth-that-still-might-be.  Our so called sister planet orbits second from the Sun. Cloudy, hot, and unhospitable to life as we know it, Venus demonstrates as well as Mars why comparative planetary science can greatly improve understanding of our own planet.

The greenhouse effect on Venus results in a poorly understood phenomena called zonal super-rotation. Hurricane winds across the cloud tops help the atmosphere to rotate much faster than the planet itself, but these winds give way to barely a breeze at the surface. The atmosphere is primarily carbon dioxide with some nitrogen. Thick sulfur dioxide clouds and other particulates conspire to hide the surface. The USSR visited the surface of Venus with several landers, some that included cameras, while orbiters with radar equipment accomplished global surface mapping last decade by orbiters. Mountains, volcanoes, pancake domes, plains, channels, and a impact craters have been discovered on the surface. The surface appears to be geologically young, despite little evidence for plate tectonics, the process on the Earth that recycles old crust and exudes new crust. The youthfulness of the Venusian surface may be due to catastrophic upheavals that periodically see the crust overturned (this might have last occurred from 300 to 500 million years ago).

After a planetary spacecraft is successfully launched on its long journey to its target planetary object, the various teams involved in the mission must checkout the instruments and subsystems they provided. This usually involves taking images to verify that everything is working properly. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) and the Venus Monitoring Camera (VMS) on board The European Space Agency’s (ESA) Venus Express successfully captured images of the Earth-Moon system and demonstrated their ability to help explore the mysteries of Venus.

VIRTIS from l’Observatoire de Paris (Paris Observatory) in collaboration with l’IASF-Rome, l’IAS-Orsay and l’DLR-Berlin captures ultraviolet, visible, and near-infrared wavelengths of light. Different wavelengths reveal different characteristics of a planetary body, such as its reflectivity, thermal properties, atmospheric details, etc. The VIRTIS observations of the Earth-Moon system were primarily meant to checkout and calibrate the equipment, but the images may also be used for scientific comparison with future images taken of Venus.

VMS from the Max-Planck-Institut für Sonnensystemforschung (Max Plank Institute for Solar System Research) took the image at the top of the page showing the Moon and Earth in (counterclockwise from the top left) infrared 1, ultraviolet, visible, and infrared 2 light. The Earth is overexposed in these images because the Moon is so much smaller and fainter and therefore its image is harder to capture.

To the left is the Earth captured by VIRTIS in visible light and to the right is the Earth in infrared, revealing its thermal radiance. Antarctica is the brightest red (indicating the weakest radiance) spotch at the bottom of the globe.

Images of VIRTIS (examples below) during laboratory calibration while still located on the Earth are located on the VIRTIS team site.

More Information

• ESA Website
  • ESA Press Release - “Earth-Moon observations from Venus Express“
  • Venus Express Mission
  • Visible and Infrared Thermal Imaging Spectrometer (VIRTIS)
  • Venus Monitoring Camera (VMS)

As viewed from the Earth, Venus is currently passing across the face of the sun, the first such transit in 122 years. The images currently coming in on various websites from amateurs and observatories in select regions of the world show a small black circle slowly making its way across the gigantic face of the sun. Scientists are using this rare occasion to test technology for observing transits of extrasolar planets across their own parent stars and to study characteristics of Venus’ atmosphere. Mysky has some first images up, as does an astronomy site in Norway and the site for the TRACE probe orbiting the Earth.

According to Space.com, the next transit will actually happen in 8 years. Due to the geometry and mathematics involved, two transits occur 8 years apart, and then there is a wait of over a hundred years for the next pair of transits.