While Planet Earth certainly offers excellent hiking and adventure opportunities, none of these involve methane river rafting, a 20 kilometre-drop from a cliff top or cryovolcanoes [link]. On the other hand, only a handful of Earth peaks would call for wearing an oxygen mask, and no destination on the home planet would require a full space suit, a portable nuclear power station or several years’ travel in a spaceship. In this article, we’ll scout out the best off-Earth hiking and extreme sports targets. No booking options yet, but already plenty of travel literature!
- The highest peak of the Solar System
Some climbers always keep their eye on the highest peaks. In the grand Solar System race to the top, our mighty Everest on Earth is maximum in the solid mid-range.
The award of the highest peak of the Solar System used to go uncontested to Olympus Mons on Mars, which also holds the prize for the highest volcano. Its base is as large as France or Arizona, so be prepared for a long trip from spaceport to the actual start of your hike. The peak is over 21.9 km (13.6 mi) high as measured by the Mars Orbiter Laser Altimeter. If you find “over 21.9km” a strange way of expressing the figure, you’re right – for the moment, we can’t give the height of Olympus Mons with the same accuracy as Earth peaks. Even on Earth, I took until the 1980s to decide conclusively the competition between Mount Everest and K2, and it took quite a lot of climbs, trigonometry and technological advance with GPS to get the figures with a margin of error within centimetres.
In the last decade, a new contester emerged for the highest mountain of the Solar System title: the Rheasilvia crater on the asteroid Vesta. Vesta is located in the Solar System’s main asteroid belt between the orbits of Mars and Jupiter. The crater is a colossal impact basin caused by collision with a smaller body about a billion years ago. It’s the biggest crater in the solar System, and the peak emerging in the center of the crater rises to approx. 22 kilometre (in other sources, 20-25 kilometres), which could be taller than Olympus Mons.
A few pointers if you have to choose between the two destinations: travel time to Vesta would be more than double compared to Mars (estimating one-way trip to Mars to take 7 months). Mars has just the ideal gravity for mountaineering: you’d weigh roughly one third of your Earth weight, so you’d feel extra fit, but it’s still strong enough to keep you from bouncing off the ground. Though some areas on Mars can experience balmy temperatures above zero Celsius, unfortunately Olympus Mons is rather freezing: count with temperatures around 60 C below zero for your hike, and it could drop to 150 C below zero on a really bad day. But then it’s not any hotter in the Rheasilvia crater, either.
In any case, Mars is almost certainly going to be the first off-planet (Earth) mountain peak to be actually climbed by humans. Estimates range from 2038 to 2070 or beyond, but it is realistically within our reach. The only easier alternative would be to send astronauts to Mount Huygens on Moon (5500 metres) – but somehow, it’s on nobody’s horizon. Just not the same vibe, I guess.
If you’re seriously after peaks, you can also consider the “Seven Summits of the Solar System” challenge [link]- the real ultimate adventure of our spot in space!
2. The deepest canyon of the Solar System
After the tallest, let’s go for the deepest. Good news is that you can combine the two: the largest canyon system in our system is Mars’s Valles Marineris. It’s nearly 10 times as long as the Grand Canyon and three times as deep. It stretches over 4,000 km (2,500 mi) across Mars just below the equator, clearly visible from the planet’s orbit. Perhaps it was formed by a huge earthquake – it must have been one hell of a crack. To give an impression of its width – if you’d be standing on one rim, the opposite rim would be way beyond the horizon!
Hiking this mega-gorge offers very favourable conditions, at least compared to other off-Earth destinations. The bottom of the canyon hides a large amount of frozen water, so you can pack light as long as you figure out the technology to extract the water from Mars rock. At its deepest point, 11 kilometres at the Melas Chasma, air pressure is the highest on the whole planet, making it one of the spots considered for future habitation. Also, the valley is close to the Equator, which is the warmest region of Mars: on the hottest day of the year, temperature can soar to 20 Celsius. Some optimists even speculate that in these warm periods, there could be liquid water at the bottom of the canyon.
Then again, with more space probes travelling further and further, there is a contender also for deepest canyon title: on Pluto’s moon Charon, Argo Chasma is estimated to be 9 kilometres (5.5 miles) deep, making it more than five times the depth of the Grand Canyon.
3. The deadliest mountain of the Solar System
This honourable title could go to many destinations in the Solar System, but Earth’s sister planet – or rather, evil twin – Venus is certainly a hard contender. Venus’s highest peak, Skadi Mons in the Maxwell Montes massif reaches 11 kilometers (6.8 miles) so it beats Mount Everest, and has some very exotic and lethal features. As the high elevation area shows up bright on the radars, the phenomenon has been called “Venus snow” or “Venus frost”, even though temperatures on Skadi Mons, the coldest spot of Venus, are still around 380 Celsius. So what brightens the peaks is not water ice, but hot heavy metal “frosting”, mostly composed of toxic materials like lead sulphide and bismuth sulphide. Heavy metal could also snow from the sky, in the same form of condensed sulphides. We can only theorize how such environment looks like, but it may be stunningly beautiful. As both the lead and bismuth sulphide are a light greyish colour with a shiny, metallic lustre, one could imagine that these Venus mountaintops are glimmering silver in the sunlight.
Stunning or not, what you should not expect on such as hike is actual hiking. Probably the most walking you’d do would be climbing into some kind of nearly-indestructible, yet to be invented extravehicular activity (EVA) unit that can survive landing in the Maxwell Montes. Because it’s the deadliest mountain for a reason. Venus’s atmosphere is extremely toxic, consisting primarily of carbon dioxide and some other non-breathable, corrosive gases. Even the balmy +380 C of the peak altitudes is hot enough to melt lead, and it’s even hotter on the surface. Atmospheric pressure is significantly higher than on Earth, comparable to one kilometre deep in the ocean. There are very strong winds, sulphuric acid rain and lightning storms driven by volcanic eruptions. Venus is such a terrible place that it doesn’t even have a moon!
4. The tallest cliff of the Solar System
Good news for enthusiasts of base jumping and face climbing: the biggest cliff face of the Solar System has various estimates, from 7 kilometres to astounding 20 kilometres. Whether you would rather climb up or jump off a cliff which is more than twice the height of Mount Everest, Verona Rupes is the place to go. This towering cliff is located on Uranus’ moon Miranda, a small moon with very low gravity. In fact, gravity is so low that if jumped or fell from the cliff top, it would be a looong time before you hit the bottom; depending on the high estimate used, it could take full 8-12 minutes. It may remind you of the famous scene in Clarke’s Rendezvous with Rama where a crew member is forced to jump off a 500-metres cliff, using nothing more than his shirt as a makeshift parachute, and lives to tell the tale. But now we are talking about a jump 40 times as high, and without the benefit of atmosphere (rendering parachutes useless) or arriving into water. So for Verona Rupes, the way to go would be something awaiting you at the bottom, like a big pile of airbags to crash into. Or just choose the bungee jumping option. With gravity that low, after your first drop of 12 minutes, subsequent ups and downs could go on for at least an hour. Just be careful not to vomit in your spacesuit!
Some spoilsports occasionally tell us that based on the little evidence we have, it is impossible to be certain of the cliff face’s steepness, and instead of jumping from Verona Rupes, at most you could slide down. While a 7 (or 20) kilometre-long slide at low gravity also sounds like fun, for the next vertical cliff, head to Argo Chasma on Pluto’s moon, Charon. Current estimates say it has cliff faces up to 9 kilometres high. For more rarity value, Charon is a giant for a moon, while its parent planet, Pluto is officially a dwarf – making them so close in size that they are considered as our neighbourhood’s only double (dwarf) planetary system.
5. The largest ridge of the Solar System
Have you ever dreamed walking around the Equator? On Earth, it’d be rather unrealistic: given the distance, it would take you about two and a half years, but only if we assume you can walk on water, as about 80% of the route would be on ocean surface.
But don’t lose heart, you could try to bring the dream to reality on Saturn’s moon Iapetus. Its Equatorial Ridge is located exactly on the moon’s equator, and it spans for more than 75% of the moon’s entire circumference! This ridgeline features both craters and peaks, some of the latter rising 20 km above the surrounding plains, which also makes them some of the tallest mountains in the Solar System. The overall length of the tour is 1300 km, so you could walk it in about a month – making it just the ideal hiking holiday. The moon also boasts water ice, largely reducing your cargo weight, and the views form the ridge would be more than spectacular. Saturn has 83 (known) moons, and even if not all of them can be seen form Iapetus, a night sky display of dozens of moons must be something of another world. In addition, Iapetus happens to be the only moon from where mother planet Saturn’s rings are clearly visible – just make sure you also look in front of your feet from time to time!
6. Watch hell freezing over on the most bizarre moon of the Solar System
If you want to see when hell freezes over, head to Jupiter’s moon, Io. Every 42 hours, this large moon passes into giant gas planet Jupiter’s shadow, which blocks the sun out completely, and causes a sudden temperature drop. Io’s very thin atmosphere, mostly composed of sulphur dioxide, freezes in an instant, and the sulphur dioxide falls onto Io’s surface as a frost.
After two hours in the shade, Io emerges from the eclipse, and the sulphur dioxide ices sublimate back into the atmosphere. It must stink to high heaven – sulphur dioxide smell has been compared to burnt matches, rotten eggs or skunk – and instead of small quantities, on Io it is mass produced by huge plumes erupting from the moon’s many volcanoes.
Luckily, no one would dream of venturing onto Io without a super-durable spacesuit, so the smell would be the least of your problems. Because Io is so close to Jupiter, it is in the middle of the planet’s radiation belt. The moon gets hit with about 3,600 rems of radiation every day, more than triple the lethal dose, so you would need a space suit with lots of radiation shielding.
The moon boasts many attractions. Io is the most volcanically active place in the Solar System, with over 400 active volcanoes. It is extremely photogenic: volcanic plumes and lava flows paint the surface in various subtle shades of yellow, red, white, black, and green. In NASA’s evocative description, “the surface is covered with melted cheese and splotches of tomato and ripe olives”. Rotten oranges is another image frequently suggested, and it certainly pairs well with the pungent smells of sulphur.
Hiking options are abundant: Io’s mountains average 6 km in height and reach a maximum of approximately 18 km at South Boösaule Mons, which is consequently among the top highest peaks in the whole Solar System.
7. The best rafting adventure of the Solar System
The only known liquid canyon outside Earth is located on Saturn’s moon, Titan. Vid Flumina is a river of liquid methane and ethane, flowing into a large liquid methane/hydrocarbon sea, Ligeia Mare. A pretty blue river flowing into a pretty blue sea: it must look very picturesque. Scientists think the river has rapids, whirlpools and waterfalls, just like rivers on Earth, making it a prime destination for off-Earth rafting.
Titan, as the name suggests, is a giant moon, bigger than the Solar System’s dwarf planets. It has a dense atmosphere of nitrogen, an actual climate, including wind and rain. This and the presence of stable liquid formations create surface features surprisingly similar to those of Earth, such as dunes, rivers, lakes, seas and deltas. It’s just that all the components are wrong – instead of breathable air, the atmosphere is mostly nitrogen, and instead of water, the liquids are mostly methane.
In spite of the flowing rivers and lakes, Titan is a very cold world, with average temperatures around -180 C (94 K, −290 °F). It’s also very dark there due the hazy atmosphere, letting only about 0.1% of the amount of light Earth receives to the surface. So bring a good torch for the methane river rafting, and be prepared for frequent methane rains!
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