Giant bugs on Venus? It sounds like science fiction, but it's not. Scientists have found dozens of bugs measuring as large as 41 miles across living on Venus. But they don't fly, sting or even crawl. Why? Because they're not living creatures. They're volcanic structures whose appearance has earned them a nickname among the scientists who observe them: ticks.
Also referred to as "scalloped margin domes," ticks were first discovered in 1990 when the Magellan Spacecraft collected image data of a unique volcanic edifice on the Venusian surface. The structure consisted of a collapsed dome approximately 22 miles in diameter. A few short ridges radiated from its perimeter, and a pool of collapsed lava flows connected to its western base. In these features, scientists saw what resembled the body, legs and head of what they called "The Tick" after the infamous insect.
In the year that followed, many more ticks were found populating Venus' landscape. So far, about 50 ticks have been found. But despite their abundance, their formation remains a mystery. One theory suggests that they were once what are called "pancake domes," broad, circular volcanoes with steep edges and flat tops. Over time, they would have endured heavy erosion resulting in the tick-like domes we see today.
More surprising yet is that just next door to Venus, the planet Mercury is home to another giant bug -- the ticks' arachnid neighbor, Pantheon Fossae. First observed in 2008, Pantheon Fossae consists of an impact crater more than 25 miles wide called Apollodorus and a series of surrounding troughs -- a system that looks like the abdomen and legs of a spider.
The existence of these "bugs" illustrates the wealth of geologic surprises found in our solar system. The next time you see an image of a planet or moon, search for your own bug look-alikes in the features carved into their surfaces.