<P> A solar transit of Venus is an extremely rare event, and the last solar transit of the planet before 2004 was in 1882 . The most recent solar transit was in 2012; the next one will not occur until 2117 . </P> <P> The Venus Express spacecraft formerly in orbit around the planet probed deeper into the atmosphere using infrared imaging spectroscopy in the 1--5 μm spectral range . </P> <P> The JAXA probe Akatsuki, launched in May 2010, is studying the planet for a period of two years, including the structure and activity of the atmosphere, but it failed to enter Venus orbit in December 2010 . A second attempt to achieve orbit succeeded 7 December 2015 . One of its five cameras known as the "IR2" will be able to probe the atmosphere of the planet underneath its thick clouds, in addition to its movement and distribution of trace components . With a highly eccentric orbit (periapsis altitude of 400 km and apoapsis of 310,000 km), it will be able to take close - up photographs of the planet, and should also confirm the presence of both active volcanoes as well as lightning . </P> <P> The Venus In - Situ Explorer, proposed by NASA's New Frontiers program is a proposed probe which would aid in understanding the processes on the planet that led to climate change, as well as paving the way towards a later sample return mission . </P>

Why does venus have a dense carbon dioxide atmosphere