<html>
<p>Venus and Earth are almost twins in mass and sizes. But here similarites end. For many years scientists have been frustrated by their inability to understand Venus tectonics and why it is so different from Earth's. </p>
<p> A team of planetary scientists has created a physical model of part of the surface of Venus and in so doing may have solved the mystery of tectonics on Venus.</p>
<p><img src="https://img-fotki.yandex.ru/get/50936/28554600.3/0_1b3c4c_22f2526e_XL.jpg" width="800" height="800"/></p>
<p>Image: NASA/JPL Venus map, composed by Magellan probe</p>
<p>The greatest mistery of Venus is that it totally lacks plate movement - one of the main Earth's features. (the large number of craters suggest that there is no churning). But giant trenches, looking like Earth's subduction zones (collisions between two of Earth's tectonic plates, where one plate sinks into the mantle underneath the other plate ) have been observed.</p>
<p>All of the factors that go into defining how a planet's crust look are too complex to be modeled on a computer accurately, so the researchers took a different approach—they created a physical model. A particular interest of this study was to obtain explanation the way that unique features - volcanic like features - coronae are formed. Coronae are circular depressions with bulges in the center, surrounded be trenches.</p>
<p><img src="https://photojournal.jpl.nasa.gov/jpeg/PIA00109.jpg" width="1250" height="1000"/></p>
<p>Image: <a href="https://photojournal.jpl.nasa.gov/catalog/PIA00109">NASA/JPL</a> The corona has a diameter of 97 kilometers. The proposed name for the corona is Idem-Kuva, a Finno-Ugraic harvest spirit<br>
The model is simple. Researchers placed some finely ground sand in the bowl, added water and then heated it from below.</p>
<blockquote> In heating their bowl of mud, the researchers noted that a crust formed due to evaporation at the surface and then bulges formed as hot parts below the crust forced their way upward. Eventually, the material that was pushed from below (similar to Earth mantle plumes) pierced the surface and leaked out onto the surrounding surface (rather like a pie in the oven). As material leaked out, pressure was relieved, causing the bulge to deflate even as more material made its way through the puncture wound, which soon hardened, creating a small bulge in the center of depression surrounded by trenches.</blockquote>
<p>Comparisons to real maps of Venus's coronae showed them to be very similar.</p>
<p>So, one mystery - how coronae are formed is solved.</p>
<p>But there are many other misteries left: In the period from 1 billion to 500 million years ago, almost all surface was covered by basalt lava from the enormous volcanic eruptions. Only few mountaneous regions - tesserae, are free of lava. Unfortunately, all surface probes (Soviet Venera series in 1980th) landed in basalt areas. </p>
<p><img src="https://img-fotki.yandex.ru/get/195431/28554600.3/0_1b3c4e_bdc924ab_XL.jpg" width="800" height="600"/></p>
<p>Image: Venera-10 landing site, with perspective, corrected by Don Mitchell Oct 25, 1975.</p>
<p>Landing in the tessera area can give keys to understanding what happened on the Venus 1 billoion years ago an why histories of Earth anv Venus went apart.</p>
<p>This mistery can solve lander of the future spacecraft Venera-D being developed by Russia Roscosmos, with launch planned to 2025.</p>
<p><img src="https://img-fotki.yandex.ru/get/94596/28554600.3/0_1b3c4f_787bc072_XL.jpg" width="800" height="602"/></p>
<p>Image: IKI/RAN</p>
<p><br></p>
<p><br></p>
</html>
hiveblocks