4 Unexpected Discoveries On Solar System Planets

4 Unexpected Discoveries Made in the Solar System

Only a few decades ago, around the middle of the twentieth century, we were just beginning to physically travel into the solar system. But a lot has changed (and advanced) since then! Today, we’ve landed various spacecraft on the moon, and we’ve sent various machines to other planets. We’ve landed probes on asteroids, and even visited comets, in what has been quite the golden age for space exploration. Yet, despite all the knowledge we’ve undoubtedly gained, space never fails to surprise.

This is Unveiled, and today we’re exploring four of the most unexpected discoveries made in the solar system.

On Earth, the slow movement of the land beneath our feet is a continuous process. Sometimes, via earthquakes, it can cause huge amounts of destruction… but, ultimately, over the course of millions of years, it also leads to transformation. Ensuring that this world we call home never stays the same for too long. But so many of the other solar system planets have undergone massive change over their own histories, too, even if wholly Earth-like tectonics aren’t currently seen elsewhere. In the case of one planet, though - Mercury - we’ve come to realise something in particular. Today’s first unexpected discovery… that Mercury is shrinking.

Mercury’s nature best came to light through NASA’s MESSENGER space probe mission, which orbited the planet between March 2011 and April 2015. It conducted an extensive survey of the Mercurian surface, most notably revealing what NASA refers to as small, cliff-like structures all over it, called fault scarps. An already tiny planet compared to the rest of the solar system, Mercury has only around 300 miles worth of mantle and outer crust to play with… but we know that it’s shrinking anyway, because it’s believed that those fault scarps only form when the crust reacts to an inner core that’s reducing in size, which happens as the core cools down over millions of years. The true extent of Mercury’s shrinkage, however, is still debated. Around the time of the MESSENGER mission, scientists were suggesting about an eight-mile loss from its diameter. Since then, it’s been argued that the loss is less than that. But, either way, the future of Mercury becomes much more puzzling when we know that it’s actively reducing in size.

Our second unexpected discovery takes us much further away from the sun, past Venus, Earth, Mars, and the Asteroid Belt, to the gas giants of Jupiter and Saturn. Among other things, these planets host some of the largest and most violent planetary storms in the solar system. The Great Red Spot of Jupiter is one example, having been in the spotlight since it was first observed in the 1600s. And we do know of other, similar storms, too, detected on the surfaces of the ice giants, Uranus and Neptune. Much like the storms we’re accustomed to on Earth, these space weather events almost always appear to be circular or spiral in shape. In an unexpected twist, however, astronomers know of a completely different shape of storm over Saturn’s north pole. Thanks to its six distinct sides, it’s widely known as Saturn’s Hexagon.

Saturn’s Hexagon was first discovered in 1987 by one David Godfrey, an astronomer who was working on data taken from the Voyager mission six years earlier, in 1981. High-resolution images of this unusual atmospheric feature weren’t available until decades later, though, when NASA’s Cassini mission orbited Saturn for thirteen years between 2004 and 2017. Now, we can see with clarity just how bizarre this Saturnian structure really is… but is there any explanation for it?

Well, there have been various studies held, but really this particular storm remains something of a mystery. Many hypotheses centre on how the swirling vortex clearly seen at the Hexagon’s centre could be interacting with the surrounding atmosphere of Saturn as a whole… with various models tested over the years to show that, weird as it may seem, a hexagonal shape is possible. Meanwhile, debate is also ongoing over how deep the storm really is, with some contending that it’s hundreds of miles deep, while others claim it could be many thousands of miles from top to bottom. One thing that is for sure is that this is one storm you do not want to be caught in the middle of!

But, moving onto our third unexpected discovery, and we of course know that, aside from the Hexagon, Saturn is more classically known for its iconic rings. We also know that over recent decades we’ve confirmed ring systems around some of the other solar system planets, too, including all the remaining outer planets - Jupiter, Uranus, and Neptune. Nevertheless, it came as a surprise when astronomers working at the National Observatory in Brazil, in 2014, found another ring system… but this time around a much smaller object. Around an asteroid named Chariklo.

Orbiting the Sun between Saturn and Uranus, Chariklo is the first non-planetary object confirmed to have its own ring system. It was spotted during a study led by one Felipe Braga-Ribas, during which this unusual cosmic formation was actually only seen for a few seconds - when it passed in front of a distant star. Chariklo and its rings caused that star to briefly dim, and scientists were able to discern from their readings that while the asteroid itself was about 150 miles wide, it also hosted two distinct rings - an inner ring that’s about four miles wide, and an outer one that’s around two miles wide. Much like the rings of Saturn, which are thought be many to be the remnants of a one-time moon, it’s been hypothesized that the fragments around Chariklo may also have once formed a larger, more complete astronomical body. Although, we can’t yet be certain.

But, finally, our fourth unexpected discovery is also wrapped up in one of the most long-awaited discoveries yet to be made in all of science: alien life. While we may not have had huge success in our search for aliens to this point, it could be that one discovery on a Saturnian moon ends up changing everything. For once, we’re not here referring to Titan, the largest and typically most popular of Saturn’s moons. Rather, we’re interested in another of the 80-plus natural satellites that orbit this furthest gas giant, the sixth largest of all Saturn’s moons: Enceladus.

Though it was discovered as far back as 1789, by William Herschel, Enceladus remained a mostly unknown world until, again, the Cassini probe. Beginning in 2005, it performed multiple flybys of this most enigmatic of moons, revealing to the world its spectacularly icy surface and securing its reputation as the most reflective body in the solar system. Despite the Cassini mission ending in 2017, however, surprising details continue to be reported from the data it collected.

For example, a 2019 study by a team at the Free University of Berlin, led by Doctor Nozair Khawaja, confirmed the existence of organic compounds on Enceladus, similar to those on Earth that are vital for life. This is potentially a hugely significant discovery, with Doctor Khawaja explaining that; “If the conditions are right, these molecules coming from the deep ocean of Enceladus could be on the same reaction pathway as we see here on Earth”. The key thing here is that Enceladus is showing more and more that it hosts the ingredients for amino acids, which are the building blocks for life as we know it. In a statement at the time, Khawaja continued that; “we don’t yet know if amino acids are needed for life beyond Earth, but finding the molecules that form amino acids is an important piece of the puzzle”. Today, thanks to studies like this, Enceladus is now seen by many as top-of-the-list when it comes to potential homes for extraterrestrial life.

The discovery itself was made possible thanks to state-of-the-art instruments onboard Cassini, which measured the ice and vapor emitted in cryovolcanic plumes, shooting out from Enceladus’ surface. The findings suggest complex, hydrothermal environments on Enceladus… and, maybe, conditions similar to what we see in the deep ocean vents here on Earth. Perhaps, then, this far-off moon, orbiting the ever-mysterious planet of Saturn, could also be considered the most Earth-like other world discovered in the solar system so far. Only time will tell, but the realisation that it might be has caused the eyes of the scientific world to look in an all new direction.

For now, so, so much of the solar system remains to be better explored and better understood. There’s a lot of work and study in front of us. And in the years to come, with the vast expansion of space programs all over the world, we will surely uncover more surprises. Until then, though, those are four of the most unexpected discoveries made in the solar system.