Venus’s strange plateaus may sparkle. Our neighbouring world is sprinkled with domes several hundred metres high that appear different from the rest of its surface, and they may be made of shiny “crystal mush” that is squeezed up from underground.
Most of Venus’s surface is flat, shaped by lava that has flooded the land over the planet’s history. But amid these relatively unremarkable lava flows sit domes with unexpectedly steep sides that have confused researchers for decades, because it seems unlikely that they were produced by the same dominant processes that shaped the rest of the surface.
Geoffrey Bromiley and Sally Law at the University of Edinburgh, UK, have come up with a potential solution. They think the steep-sided domes are probably formed by lava that is thicker – more viscous – than the runny lava that floods the rest of the surface.
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“If you poured olive oil onto the table, it would just flow away and run all over the table, and you’d still have a flat surface,” says Bromiley. “If you poured something a lot thicker, like peanut butter, that would stay there and form a dome on the table.”
That thicker substance could come in the form of a crystal mush similar to what makes up some landforms that the researchers studied in Cyprus, he says. The mush that made up those hills is full of green olivine crystals up to 1 centimetre in size.
Those large crystals form while magma is still deep underground. They are then left behind when the rest of the still-liquid magma rises up through the crust because it is hotter and more buoyant than the surrounding rock, says Bromiley. But when faults rip the planet’s crust apart, the crystallised magma mush can be squeezed out like toothpaste from its tube.
“At Cyprus, we see these faults that allow the mush to get to the surface, and we’re suggesting the same thing could happen on Venus,” says Bromiley. “What we’d see on Venus would depend on the depth at which the magma is cooling, but it’d be filled with very pretty rocks with big green or red crystals.”
This explanation, unlike some others, would explain why the domes tend to be near other volcanic landforms, because they would come from the same process. It could be tested with the next generation of Venus orbiters, says Bromiley.
Icarus
