For Earth-bound optical telescopes , the surface of Venus is shrouded beneath thick clouds made mostly of carbon dioxide . To penetrate this veil , probes like the Magellan spacecraft use radar to reveal remarkable features of the planet , such as mountains , craters , and volcanoes . But now , astronomers have combined the Green Bank Telescope with the radar transmitter at the Arecibo Observatory to make remarkably detailed images of the planet 's surface from Earth . Pictured is a projection of the radar data of Venus collected in 2012 . Striking surface features , like mountains and ridges , are easily seen . The black diagonal band at the center represents areas too close to the equator to obtain well-resolved image data . The radar signals from Arecibo in Puerto Rico passed through both Earth 's atmosphere and the atmosphere of Venus . Here they hit the surface and bounced back to be received by the Green Bank Telescope in West Virginia in a process known as bistatic radar . This capability is essential to study not only the surface as it appears now , but also to monitor it for changes . By comparing images taken at different periods in time , scientists hope to eventually detect signs of active volcanism . They believe images such as this could also reveal other dynamic geologic processes that could provide clues to Venus 's geologic history and subsurface conditions . Spanish astronomers have revealed a new theory for a ' Y ' shape on Venus ( annotated image from the Pioneer Venus Orbiter in 1979 shown ) . They say it is formed by winds pushing a 'wave ' of clouds on the planet . These winds move faster at higher altitudes , creating the odd shape . 'It is painstaking to compare radar images to search for evidence of change , ' said Bruce Campbell , a senior scientist at the Smithsonian 's National Air and Space Museum in Washington , . 'The work is ongoing . In the meantime , combining images from this and an earlier observing period is yielding a wealth of insight about other processes that alter the surface of Venus . ' Venus is slightly smaller than Earth but has a similar mass . It is the second closest planet to the sun at a distance of about 67 million miles ( 108 million kilometres ) , and takes about 225 days to orbit the sun . One day on Venus lasts as long as 243 Earth days . Its thick and toxic atmosphere is made up mostly of carbon dioxide and nitrogen , with clouds of sulphuric acid droplets . It 's believed that its atmosphere contributed to a runaway greenhouse effect that made the planet inhospitable . The planet 's extreme high temperatures of almost 480°C ( 900°F ) make it seem an unlikely place for for life as we know it . High-resolution radar images of Venus were first obtained by Arecibo in 1988 and most recently by Arecibo and GBT in 2012 . When astronomers first started taking images of Venus , they were somewhat baffled by a mysterious ' Y ' shape that covered the entire planet . Last week researchers say they have an answer - high intensity winds are distorting a 'wave ' of clouds to produce a stretched effect . The discovery could also reveal how similar processes take place on other slow-rotating bodies in the solar system . The latest theory was proposed by astronomers from the Institute of Astrophysics of Andalusia ( IAA-CSIC ) in Granada , Spain , in collaboration with the university of the Basque Country and the Institute of Astrophysics and Space Sciences of Portugal . On Venus strong winds move the upper atmosphere 225 mph ( 360km/h ) , circling the planet every four to five Earth days . But the planet itself takes almost 243 Earth days to complete an orbit - meaning the winds are much faster than the rotation speed of the planet . The winds have a mostly constant speed at different latitude , but nearer the pole they circle the planet quicker as the circumference of the planet is smaller . This ultimately gives rise to this ' Y ' shape , as the clouds at the top and bottom of the shape are moved more quickly . To take the stunning images , astronomers combined the Green Bank Telescope ( right ) in West Virginia with the radar transmitter at the Arecibo Observatory ( left ) in Puerto Rico .
Astronomers took images with Green Bank Telescope in West Virginia . They combined this with the radar transmitter at the Arecibo Observatory . By comparing images , scientists hope to detect signs of active volcanism . about 225 days astronomers revealed a new theory for a ' Y ' shape on Venus . They say it is formed by winds pushing a 'wave ' of clouds on the planet .