Guest Contributor – Ralph Storer

Introduction

If readers would like to contribute an article for the Guest Contributor page heading please contact me, my email address appears on the About Me page heading.  The 0nly two things I ask is that the article should be hill related and importantly I should not end up in court through its publication!  Otherwise the choice of subject matter is down to the Guest Contributor.

About the Author; Ralph Storer

RALPH STORER is an experienced hillwalker who has hiked extensively around the world.  Despite being a Sassenach by birth, he has lived in Scotland since studying psychology at Dundee University and has a great affinity for the Highlands.  He is the author of the acclaimed Ultimate Guide to the Munros series of guidebooks among others.  As well as disappearing into the hills for a regular fix of nature, he also writes novels and sexological non-fiction, and produces darkwave music on his home computer.

Hillwalking on Pluto

by Ralph Storer

I’ve always been fascinated by the notion of hillwalking on other planets.  If nothing else, it makes you realise how lucky we are down here in this part of the solar system.

We take our mountains for granted.  We’ve evolved in their shadow, in fact from the same cosmic material.  Relative to the human life span, they’re immutable.  The Himalayas may rise a little each year as tectonic plates collide, but we don’t notice it.  All our favourite mountains are being eroded and will one day become flat, perhaps to be reborn as other mountains, but we don’t notice that either.  I’m fairly confident that my guidebooks will remain viable for a while.

Studying other planets raises many interesting questions about our own, including how we measure the height of our mountains.  We take for granted that the true height of a mountain is its height above sea-level (whether measured by a tide-gauge or the geoid).  This means that when the oceans rise or fall significantly, as they have in the past and will do so again in the future, the heights of our mountains vary.  The sea-level today is around 130m higher than it was during the last Ice Age.  Does that mean the mountains are 130m lower?  Perhaps, but what if there is no sea, as on the moon?

In The Joy of Hillwalking I give the example of the crater Theophilus, which is 4,400m deep.  The mountains in the centre of the crater rise 1,400m above their base but are dwarfed by the crater rim and surrounding plain.  What is the true height of these mountains?

One possible measurement is the distance from the centre of the planet to the summit.  This can produce counter-intuitive results because planets are not perfect spheres.  Ours bulges at the equator, which makes the summit of Chimborazu, an Ecuadoran volcano 6,263m above sea-level, the highest point above the earth’s centre.

A second option is to calculate the average height of a planet’s surface, measured as the mean radius from the centre, and base elevations on that.  The highest point on the moon, as measured by altimetry from orbiting spacecraft, is 10,786m above the mean radius.  Relative to an average height, however, half of all elevations will by definition have a negative figure, which is not going to help define the climbing potential of mountains located inside a deep crater.

A third option is to choose a more or less arbitrary figure.  Maps of the moon and Mars currently use gravity to provide a base level similar to sea-level on earth.  On Mars the base level is taken to be the height at which atmospheric pressure is 6 millibars – the triple point of water, at which it can exist as gas, liquid or solid.

 

US astronauts John Watts Young and Charles Duke set a lunar altitude record in 1972 when they landed on the Descartes Highlands at a height of 7,830m. Of course, they didn’t walk there.  What would be a more impressive mountaineering achievement is climbing the mighty Caucasus Mountains, which rise 6,000m above the Sea of Serenity.

This gives a clue to a fourth measurement method, and one that is particularly useful to hillwalkers planning a trip: the height differential between base and summit.  This is known as topographical prominence in the US but is more correctly termed denivelation.  French guidebooks regularly specify a denivelation figure, but the term remains surprisingly little used in the English-speaking world.

Using denivelation as a measure, Alaska’s Mount McKinley, which rises 6,000m above its base, is ‘higher’ than Mount Everest, which rises less than 3,000m above its Nepalese base camp.  If there were no terrestrial seas, both would be eclipsed by a currently unnamed seamount (submarine mountain) near the Tonga Trench, between Samoa and New Zealand, which rises 8,700m above the ocean floor.  It’s about time this secret but mighty mountain was given a name.

Again using denivelation as a measure, Mars has even greater mountaineering potential than the earth or the moon.  The summit of Mons Olympus volcano towers 25km above its base, making it until recently the solar system’s height record holder.  Apart from mighty mountains, Mars and the moon have another attraction for hiking: low gravity.  The moon’s gravity is only 0.165 that of earth, while on Mars it’s 0.376. This means that you can jump three times as high on Mars as on earth, and six times as high on the moon, as seen in film of astronauts bounding across its surface.

It sounds great, but there’s a major downside.  The atmosphere of Mars is mainly carbon dioxide, while the moon has virtually no atmosphere at all.  With no atmosphere you’d certainly have no altitude problems as on earth, but you’d have to climb with oxygen tanks anyway and that kind of puts a damper on the experience.

It’s even worse on Mercury, the nearest planet to the sun.  This is a completely dead world with no atmosphere and no weather.  Its mountains rise to 3,000m in the Caloris Range, but because the planet spins very slowly the side facing the sun heats up to 427ºC. Don’t forget to pack the sunscreen.

Venus is the most earthlike planet in size, with a gravity that’s 0.907 that of earth and peaks that culminate with a denivelation of 6,400m at Skadi Mons in the Maxwell Mountains.  However, would you want to climb somewhere that has an atmosphere of carbon dioxide, is always enveloped in cloud and has a Vibram-melting surface temperature of 462ºC?

Even more of a hillwalking challenge are the outer planets of Saturn, Jupiter and Uranus.  On Jupiter wind speeds of 650kph heat the deadly atmosphere to 1,400ºC, while Saturn has even greater storms with wind speeds up to 1,800kph.  If that doesn’t dissuade you from booting up, how about this: they’re gas giants that until recently were thought to have no solid ground on which to walk anyway.

Which brings us Pluto.  Who’d have thought little Pluto, only discovered in 1930, would be so topographically interesting, especially after its demotion from planet status in 2005?  Until 2016 only fuzzy images of its surface existed, then the New Horizons spacecraft took a closer look and everything changed.

Photographs revealed a great mountain chain 3,500m high, which scientists have compared to the Rocky Mountains… except that they’re made of water ice instead of rock.  Such an incredible accumulation of ice is possible because of a temperature that can dip to -240ºC.  You’d need to pack your thermals, but imagine cramponning up such peaks.  Not only that, but on Charon, Pluto’s largest moon, a 9km-deep canyon was discovered. Eat your heart out, Grand Canyon.

Pluto’s small size gives it another climbing advantage.  Gravity is only 0.071 that of earth – 140 times less. Once you’ve bounded up the mountains you could leap from peak to peak!

I confess to taking a special interest in Pluto because the equipment that took the first close-up pictures was called Ralph.  I’ll probably never get there myself, but at least my namesake has visited.

The planets are not the only interesting places to look for climbing potential in the solar system.  Jupiter and Saturn may or may not have solid ground, but their moons do and you’ll find some sizeable hills there if you fancy spending a week or two in the backcountry.

And there’s undoubtedly still much more to be discovered.  In 2011 the Dawn spacecraft investigated Vesta, a lump of rock in the asteroid belt between Mars and Jupiter.  Despite being only 525km wide it has a crater – Rheasilvia – that’s almost as wide and whose rim stands a whole 31km above the lowest point on the crater floor.  The rim highpoint now eclipses Mons Olympus on Mars to make it the solar system’s current height record holder as measured by denivelation.

Moving further out into space beyond our solar system, real hillwalking options could be endless.  Exoplanets (planets orbiting a star other than the sun) continue to be discovered apace and some of them appear to be earthlike.  In 2013 astronomers estimated that there may be 40 billion earthlike planets in our galaxy alone.  Our nearest earthlike neighbour, discovered in 2017, is Ross 128b, a mere 11 light-years away.  On Ross 128b a year is only 9.9 days long. And you thought British summers were short.

Other exoplanets have extraordinary properties. Exoplanet HD 189733b has 8,700kph winds.  WASP 33b has a temperature of 3,200ºC. On WASP 12b it’s thought that corundum condenses in the atmosphere and rains as rubies.

Little is yet known about exoplanet topography, but there can be no doubt there’s some interesting terrain out there waiting to be explored by hillwalkers of the future.  Meanwhile, let’s not complain about our own planet’s weather ever again.

Reprint from Ralph Storer’s book See You on the Hill