The smallest planet in our solar system, Mercury, is reportedly shrinking. It is estimated that the planet’s diameter has contracted by almost 14 kilometers since it was first formed almost 4 billion years ago.
A shrinking planet
Earth’s massive mountains and steep cliffs are said to be the result of colliding tectonic plates. But in the case of Mercury, scientist believe that the planet is actually shrinking like a raisin kept out in the open for a long time. Being very close to the Sun, Mercury is doomed to a scorched existence.
Almost all planets chill and shed heat. What makes Mercury interesting is the extreme results of the activity. “The process has taken an unusual toll on Mercury’s already cratered complexion, forming cliffs that can soar up to two miles (three kilometers) high — about as tall as Mount St. Helens — and long chains of aligned ridges that snake across the face of the planet for up to 1,050 miles (1,700 kilometers), more than twice the length of Florida,” according to National Geographic.
Until 2011, the idea that mercury was shrinking had no definite proof. But the Messenger spacecraft that approached the planet that year finally provided some much-needed evidence. The craft sent numerous photographs back to Earth, showing a surface with thousands of scarps snaking along, proving without a doubt that the planet had shrunk from its initial formation.
However, scientists are not too sure on whether the rate of shrinking has slowed down or if the process itself has stopped. To solve this, a craft will have to land on the planet and stay there for a very long time. Considering that Mercury’s surface temperature is around 430°C, scientists do not see such a mission happening anytime soon.
“The only way that we would know for sure that it’s not [contracting] is if we had seismic instruments on the surface that were able to listen for thousands of years and not detect earthquakes that we could attribute to the planet creaking and cooling… I don’t think there’s any measure we could make that would reliably tell us for sure the process has ended,” Paul Byrne, a planetary geologist who led the Messenger study, said to The Atlantic.
A new mission
In October this year, the European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) collaborated to send a new mission to Mercury. The BepiColombo is the first mission to the planet since NASA’s Messenger. BepiColombo is a fusion of JAXA’s Mercury Magnetospheric Orbiter (MMO) and ESA’s Mercury Planetary Orbiter (MPO), both of which are equipped with the latest scientific instruments needed to study the planet.
“Beyond completing the challenging journey, this mission will return a huge bounty of science… It is thanks to the international collaboration and the decades of efforts and expertise of everyone involved in the design and building of this incredible machine that we are now on our way to investigating planet Mercury’s mysteries,” Jan Wörner, ESA Director General, said in a statement (SyFy Wire).
The MMO will enter a high orbit while the MPO will settle in a lower orbit around Mercury from where it will image the planet’s surface. The orbiters have a strong anti-radiation insulation that will keep them protected from the harsh effects of the sun.