New View of Venus Reveals Previously Hidden Impact Craters

Think of the Moon and most people will imagine a barren world pockmarked with craters. The same is likely true of Mars albeit more red in colour than grey! The Earth too has had its fair share of craters, some of them large but most of the evidence has been eroded by centuries of weathering. Surprisingly perhaps, Venus, the second planet from the Sun does not have the same weathering processes as we have on Earth yet there are signs of impact craters, but no large impact basins! A team of astronomers now think they have secured a new view on the hottest planet in the Solar System and revealed the missing impact sites.

Conditions on Venus

Venus is the second planet from the Sun and, whilst it’s often called Earth’s sister planet, the reality is really they differ in many ways. The term comes from similarities in size and composition yet the conditions on Venus are far more hostile. Surface temperatures far exceed the boiling point of water, the dense atmosphere exerts a pressure on the surface equivalent to being 3,000 feet under water and there is sulphuric acid rain in the atmosphere! Most definitely not a nice place to head to for your next vacation.

Understanding the Missing Craters

If you were to stand on the surface of Venus you would see beautifully formed craters. Looking down on the planet from orbit you would see none due to the thick, dense atmosphere. Yet, if you could gaze through the obscuring clouds you would see a distinct lack of larger impact basins of the sort we are familiar with on the Moon. Now, a team of researchers mostly from the Planetary Science Institute believe they solve the mystery of the missing craters.

Mapping Haastte-baad Tessera

They have mapped a region of Venus known as Haastte-baad Tessera using radar technology and the results were rather surprising. The region is thought to be one of the oldest surfaces on Venus and is classed as tessera terrain. This type of feature is complex and is characterised by rough, intersecting ridges to create a tile-like pattern thought to be the result of a thin but strong layer of material forming over a weak layer which can flow and convect energy just like boiling water. Images from the area in question reveal a set of concentric rings over 1,400 km across at their widest. The team propose that the feature is the result of two back-to-back impact events. "Think of pea soup with a scum forming on top," said Vicki Hansen, Planetary Science Institute Senior Scientist.

Geological Insights

Obviously there is no pea soup on Venus but instead, the thin crust layer formed upon a layer of molten lava. Venus of today has a thick outer shell called a lithosphere which is about 112 km thick but when Venus was younger, its lithosphere was thought to be just 9km thick! If an impactor struck the hot young Venus then it’s very likely it would have fractured the lithosphere allowing molten lava to seep through and eventually solidify to create the tesserae we see today.

The Hypothesis of Concentric Rings

The features found suggesting that two impact events occurred consecutively, where the initial impact led to the fragmentation of the lithosphere, allowing molten lava to rise. This lava later solidified and created the distinct tessera patterns observed today. The concentric rings' study could provide significant insights into understanding not only Venus but also other celestial bodies exhibiting similar geological features.

References and Further Reading

• Impact craters were hiding in plain sight, say researchers with a new view of Venus
• NASA: Venus Overview
• Universe Today: Articles on Venus
• Science Daily: New Insights on Venus

“The research into Venus's surface is pivotal for unlocking the secrets of its geological history and understanding the impact processes on other planets within our solar system.” – Dr. Vicki Hansen