Venus may have Earth-like lithospheric thickness and heat flow


Poor old Venera 9, the Soviet Union's Venus lander, separated from its orbiter and made a hot, violent descent through the dense Venusian atmosphere on October 22, 1975, landing hard on a circular shield designed to crumple and absorb the impact. It only survived the intense surface conditions for 53 minutes, transmitting data regarding clouds, light irradiance, temperature and atmospheric chemistry, as well as the first image ever taken of the surface of another planet. And then it died. But its findings were significant because Venus and Earth are similar terrestrial planets believed to have formed through similar processes.

It's fair to say that while Earth and Venus are siblings, with comparable size and composition, they are vastly different in character. Earth harbors conditions amenable to life; by contrast, describing Venus as inhospitable is a hilarious understatement.

Venus's atmosphere, the densest and hottest of the four terrestrial planets, consists primarily of carbon dioxide with pressure at the surface about 92 times the sea level atmospheric pressure on Earth. The mean planetary temperature hovers around 464 degrees Celsius (867 degrees Fahrenheit). Pretty bad! And while it does not have a moon, even if it did, the dense clouds of sulfuric acid that shroud the entire planet would obstruct any idyllic nighttime views.

Another trait Venus shares with Earth, however, is that it sheds interior heat into space. Geologists know that plate tectonics drive interior heat loss on Earth, radiating heat at the sites where plates pull apart, but little is known about the interior dynamics of Venus.

Now, researchers at the Jet Propulsion Laboratory in Pasadena, California, have conducted an analysis of data gathered by the Magellan spacecraft in the 1990s to calculate the thickness of the crust on Venus. Their results indicate that despite their vastly different personalities, Earth and Venus have comparable heat flow and similar lithospheric thickness; this places constraints on Venus' evolution and interior dynamics. The results are published in Nature Geoscience.

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