Venus Does Have Craters. Here’s one

Venus Does Have Craters. Here’s one
By Evan Gough

As most everyone knows, Venus is called Earth’s twin, though its scorching temperatures and extreme surface pressure are more like an evil twin. For a twin and our closest planetary neighbour, we don’t know it very well. Venus’ dense clouds keep the planet’s surface hidden in visible-light observations.

It wasn’t until NASA’s Magellan spacecraft visited the planet in the early 1990s that we obtained a radar map of the surface. The survey showed almost 1,000 craters on the planet’s surface, finally visible through the sulphuric acid clouds that shroud the planet.

The leading image shows the Dickinson Crater, a 69-kilometres (43 mi) diameter crater located in the Atalanta Planitia Region. The image is from 1996 and comes from the Magellan spacecraft. NASA re-released this image to whet our appetites for two upcoming missions to Venus: the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission and the Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy (VERITAS) mission.

Dickinson crater is complex and has a partial central ring caused by gravitational equilibrium. Only large impacts produce this type of crater. The floor of the crater contains both radar-bright and radar-dark materials. Radar-bright materials surround the crater on all sides except the west, suggesting that the impactor travelled an oblique path into the surface. Scientists think the bright material can be either impact melt or volcanic material released after the impact.

Dickinson Crater is named after the poet Emily Dickinson. It’s on the very upper right (yellow) in this USGS geologic map of Venus’ Atalanta Planitia. Image Credit: USGS/NASA

85% of Venus’ 1,000 craters are in pristine condition. The number of craters and their preserved conditions hint at Venus’ history. Scientists think that the planet underwent a near-global resurfacing event some 300 million to 600 million years ago and that volcanic activity decayed after that.

For now, Venus’ crust is locked in place, and there’s nothing to degrade the craters. The planet doesn’t have active plate tectonics as Earth does. Active plate tectonics keeps Earth’s crust in constant motion, reshaping Earth’s surface as heat from the interior moves the planet’s plates. The plates smash into each other, subducting them and erasing craters over geological timescales.

This topographic map of Venus gives a better sense of Dickinson Crater’s location. Image Credit: NASA/USGS/Arecibo

Venus is different. Plate tectonics release heat from Earth’s mantle, but on Venus, that heat builds up. The planet goes through a cycle where the mantle heats up to a critical level until the crust weakens. Then there’s a pronounced period of rapid subduction lasting about 100 million years. During that time, the crust is completely recycled.

What’s Next for Venus?

NASA’s DAVINCI mission is an orbiter and a probe. The orbiter will image the planet’s surface in different wavelengths and is expected to reach orbit in 2031. One of DAVINCI’s priorities is to study the atmosphere, which in some ways is the planet’s defining feature.

The DAVINCI descent probe will gather data on the atmosphere and transmit it continuously as it descends toward the surface. One of the critical things about Venus’ atmosphere is its large quantity of primordial noble gases compared to Earth. Scientists think that Venus’ and Earth’s atmospheres started the same, but at some point, their evolution diverged. Scientists also believe that Venus may have had a large quantity of surface water before runaway heating and photodissociation destroyed it.

NASA’s VERITAS mission is scheduled for launch in 2028 and will give us an updated high-resolution map of Venus, including topography, spectroscopy, and radar imaging. One of VERITAS’ mission goals is to learn more about Venus’ impact history and how the planet resurfaces itself. It’ll also study volcanism and create our first surface rock composition map.

Venus’ large craters greater than 20km are named after deceased women who made significant contributions and are recognized as historical figures. Only three features predating the space age are named after men.

In honour of the late American poet Emily Dickinson (1830-1886), for whom this crater is named, we found a pro-science quote from one of her poems.

“Faith is a fine invention

When gentlemen can see,

But microscopes are prudent

In an emergency.”

Thanks, Emily. Thanks, NASA.

The post Venus Does Have Craters. Here’s one appeared first on Universe Today.

June 10, 2022 at 02:00AM
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