Buzz
Our pursuit of understanding the universe is still in its early stages, and we are continually astounded by every new discovery. There are countless enigmas left to solve, even in our own small section of the cosmos, the solar system.
10. Highest Mountain
Olympus Mons, a well-known mountain on Mars, is so massive that it makes even Mount Everest seem small. Standing at 21,900 meters (71,800 ft), this volcano has long been considered the tallest peak in the entire solar system. However, a newly found summit on Vesta, one of the solar system's largest asteroids, has now claimed the title. Known as Rheasilvia (named after Romulus and Remus's mother), it surpasses Olympus Mons by a mere 100 meters (330 ft). (Rheasilvia is the prominent peak in the center of the image above.)
Naturally, these measurements are not entirely exact. Given the minimal difference between the two, it’s not possible to definitively say that one is taller than the other. However, Vesta seems to hold the advantage so far.
While we’ve known about its presence since 1997, it wasn’t until 2011, when the Dawn spacecraft passed by, that we got our first real look at Vesta. We discovered that Rheasilvia is actually the central peak of an enormous crater. With a diameter of 505 kilometers (314 miles), this crater nearly spans the entire length of the asteroid.
Additionally, Vesta has endured significant impacts throughout its history, leaving behind numerous craters, including Veneneia. This crater, partially hidden by Rheasilvia, is about 100 kilometers (62 miles) smaller in diameter.
9. Largest Asteroid
Pallas holds the title of largest asteroid, but this is true only under specific conditions. First, we need to consider Ceres, the first asteroid discovered and by far the largest. In fact, Ceres accounts for roughly one-third of all the mass in the asteroid belt, with Pallas coming in third place at 7%. This means that even though Ceres is now classified as a dwarf planet, it can still technically be regarded as the largest asteroid.
Pallas also faces competition from the previously mentioned Vesta (seen here again). While Vesta may outweigh Pallas, making it the more massive of the two, Pallas is larger by volume. However, this title may not last, as recent Hubble images suggest that Pallas is actually a dynamic protoplanet. Instead of simply being a large mass of rock and ice, it undergoes internal changes, including shifting dark and light areas. This makes it a strong contender for being reclassified as a dwarf planet in the near future.
8. Largest Impact Crater
At present, there are three potential candidates vying for the title of the largest impact crater, illustrating how quickly our understanding of the universe can evolve as we gather more knowledge.
Interestingly, all three of these craters are located on Mars. The first is Hellas Planitia, which, with a diameter of 2,300 kilometers (1,400 miles), is the smallest of the contenders. However, it is the only one we are certain was formed by an impact.
Nevertheless, evidence from Utopia Planitia has nearly confirmed it as an impact crater as well. With a diameter of 3,300 kilometers (2,050 miles), it is considerably larger than Hellas Planitia.
It’s also possible that both of these craters are relatively small compared to the largest crater in the solar system. Known as the Borealis Basin (pictured above), it boasts a massive diameter of 8,500 kilometers (5,300 miles), nearly three times the size of Utopia Planitia. However, its status as an impact crater has not yet been confirmed. If it is, it would have been caused by an immense impact, and its formation could provide critical insights into the early development of Mars.
7. Most Volcanically Active Body
Volcanic activity is rarer in the solar system than you might think. While many celestial bodies, such as Mars and even our Moon, show evidence of past volcanic activity, only four confirmed bodies still experience it today. Along with Earth, there are three volcanic moons: Triton (a moon of Neptune), Io (a moon of Jupiter), and Enceladus (a moon of Saturn).
Among these, Io is the most active. Observations of the moon have revealed around 150 volcanoes, leading scientists to estimate that the total number could be as high as 400. This is remarkable because, given its icy surface and distance from the Sun, Io's ongoing volcanic activity is a surprising phenomenon.
The prevailing theory explaining how such a cold moon sustains a hot interior is based on internal friction. Io constantly deforms internally due to external forces—the immense pull of Jupiter and the gravitational influences of two larger moons, Ganymede and Europa. This tug-of-war creates powerful internal tides, generating enough friction to produce the heat required to fuel Io's volcanic activity.
6. Largest Object In The Solar System
The Sun, which makes up 99 percent of the solar system’s mass, is by far the largest object. However, in 2007, for a brief moment, a comet actually surpassed the Sun in size.
It wasn’t the comet itself that grew, but the coma—the cloud of ice and dust surrounding the comet. 17P Holmes, discovered in 1892 by its namesake, astronomer Edwin Holmes, has been observed intermittently ever since, though it was lost to astronomers for about 60 years between 1906 and 1964.
Comets often experience brightness outbursts, but on October 23, 2007, Comet Holmes underwent a stunning increase in brightness by a factor of half a million. This marked the largest comet outburst ever recorded, visible to the naked eye (although most observers likely mistook it for a star). Over the next month, the coma expanded, ultimately reaching a diameter of 1.4 million kilometers (870,000 miles), officially surpassing the Sun in size.
To this day, the exact cause of this outburst remains unknown, which means Comet 17P Holmes will likely continue to intrigue astronomers for many years.
5. Longest Channel
In 1989, the Magellan spacecraft was launched to explore Venus, our neighboring twin, and conduct a detailed mapping of its surface. It provided a wealth of valuable information about Venus’s geography and, in 1991, it discovered the longest known channel in our solar system. This channel, later named the Baltis Vallis, stretches approximately 6,800 kilometers (4,225 miles) in length.
It was later found that Venus has many similar channels on its surface, although none match the length of Baltis Vallis. What confounds astronomers more is how these channels were formed. Venus’s harsh conditions—surface pressure 90 times that of Earth and temperatures reaching 462°C (864°F)—limit the possible causes for such features.
Lava is currently the leading explanation—other channels on Venus seem to end in lava flows, suggesting that molten lava may have carved these channels following volcanic eruptions. These lava channels are unlike anything found on Earth, although similar features may have existed here billions of years ago.
4. Largest Lava Lake
As previously mentioned, Jupiter’s moon Io is one of the few bodies in the solar system still volcanically active—and it’s extremely active. All the molten lava has to be contained somewhere, often resulting in the creation of lava lakes. One such lake, Loki Patera, holds the title of the largest lava lake in the entire solar system.
Lava lakes are also found on Earth, though none are currently active. The largest of these is Mount Nyiragongo in the Democratic Republic of Congo, with a diameter of up to 700 meters (2,300 feet). However, geological evidence points to the Masaya Volcano in Nicaragua once having an even larger lava lake, with a diameter reaching up to 1 kilometer (0.6 miles).
This puts Loki Patera into perspective, as it has a diameter of approximately 200 kilometers (124 miles). While its surface area isn’t perfectly proportional due to its unique “U” shape, it remains an enormous feature. It’s nearly twice as large as Gish Bar Patera, the second-largest lava lake on Io, which measures 106 kilometers (66 miles) in diameter.
3. Most Mysterious Meteorological Phenomenon
As the largest planet in the solar system, Jupiter naturally showcases some of the most unusual meteorological phenomena. The Great Red Spot, the planet’s massive storm, is one such well-known feature.
Yet, another striking characteristic of Jupiter are the two red bands that run parallel across the planet. In May 2010, something inexplicable occurred with the lower band, called the South Equatorial Belt—it vanished.
This unexpected event baffled astronomers—no one could explain why it occurred. A range of theories were suggested, and by November 2010, the stripe began reappearing. Infrared images revealed that the belt was slowly regaining its reddish-brown hue, leading scientists to propose a possible explanation: Clouds made of ammonia ice formed at a higher altitude than the brown clouds, effectively obscuring them from sight.
This strange occurrence seems to happen roughly once every few decades and typically lasts around a year. Yet, there’s still much to uncover about the cause behind this phenomenon. As far as we know, it is the only instance of such an event in the entire solar system. To make things even more mysterious, Jupiter’s Northern Belt doesn’t seem to undergo the same changes.
2. Longest Comet Tail
Comet Hyakutake, often called the Great Comet of 1996, is famous for having the longest tail ever recorded, by a significant margin. The term “great comet” isn’t just for dramatic effect; although not an official term, it refers to comets that become incredibly bright and visible to the naked eye.
When Hyakutake passed by Earth in 1996, it came closer to our planet than any comet had in over ten years. As anticipated, it offered an extraordinary sight for astronomers and amateur photographers alike. However, no one could have predicted how long its tail would grow. It continued to extend until it officially claimed the record for the longest tail ever observed.
The previous record was held by the Great Comet of 1843, which had a tail spanning about 2 astronomical units—roughly 300 million kilometers (186 million miles). Hyakutake’s tail nearly doubled that length, reaching an astonishing 560 million kilometers (348 million miles).
In addition to its record-breaking tail, Hyakutake also provided us with significant insights into the formation of our solar system. Chemical analysis showed that the comet contained ethane and methane, marking the first discovery of these gases in a comet, which strongly suggested the presence of at least two distinct types of comets.
1. Oldest Asteroids
Despite years of research, the exact formation of asteroids remains a mystery. There are currently two leading theories: One suggests they formed like planets, through the collision and accumulation of material drifting in space. The other theory proposes that asteroids were once part of a planet located between Mars and Jupiter, which was destroyed, leading to the formation of the asteroid belt.
In 2008, our understanding of asteroids advanced significantly when astronomers at the Mauna Kea Observatory in Hawaii discovered the oldest-known asteroids in our solar system. These asteroids, estimated to be 4.55 billion years old, predate any meteorites found on Earth and are nearly as old as the solar system itself.
The age of these asteroids was determined by studying the color spectrum reflected from their surfaces. The analysis revealed that the three asteroids are rich in aluminum and calcium, containing much higher concentrations of these elements than any other space rock we have examined.
