Surprise: It's no longer Olympus Mons the highest
mountain in the solar system! (Olympus Mons non è piu' la
montagna piu' alta del sistema solare) In a way, we can consider November 19, 1969, as
the birth date of extraterrestrial mountaineering. It was not, to be honest, the ascent of an actual
mountain, but only the climbing of a modest lunar crater, inside which the American probe Surveyor
3 had gone to rest in April 1967. Charged with the recovery were the two Apollo 12 astronauts,
Charles Conrad and Alan Bean, the third and fourth men to touch the surface of our satellite.
The series of seven Surveyor probes, launched from May 30, 1966, to Jan. 17,
1968, were intended to prepare the ground for the astronauts' arrival by
gently landing in various lunar regions and assaying the texture of the soil,
as well as transmitting thousands of photographs of the surface.
The probe's recovery took place happily, but not without difficulty. The slope of the outer wall
of the small crater (200 m in diameter) where Survejor had gone to rest was modest, at about
15 percent, yet the presence of the lunar suit hindered the two astronauts in no small measure.
The reduced lunar gravity, only one-sixth of Earth's, rather than helping, also posed problems,
especially in balance. Thus, Conrad was the first man to fall on the moon.
In subsequent missions, as the lunar module's residence time became longer,
tumbles became a constant, with often comical effects. But at that time it was preferred not
to take risks: the recovery was completed using a mountaineering rope for belaying.
Of course, the probe was not removed completely, but only some parts were recovered, such as the
camera, some cables, and aluminum tubes, mainly to check its condition after two and a half
years in the hostile lunar environment. Incredibly, but that is another story,
a Streptococcus was found, surviving both the sterilization that took place on the ground and
the massive dose of cosmic and ultraviolet rays that rain down copiously on the moon,
which is not protected by any atmospheric shield. A second episode of lunar mountaineering already
occurred with the next mission, Apollo 14. The program included the ascent of a small crater
called Cone, about 330 meters in diameter and 120 meters high, with a 20% slope...
But once more the problems caused by the obstruction of the suits and reduced gravity were
felt. The two astronauts, Alan Shepard and Edgar Mitchell, had to stop the climb when their heart
rate reached 150 pulsations, considered excessive in those conditions by the NASA doctor in Houston.
But the Moon was just the beginning, for this particular kind of trekking to other
worlds. And surely, if we have some free time during future explorations as well,
we will find a way to devote ourselves to climbing some strange alien mountains as
well. Climbs that by the way will certainly be much less demanding than those we do on Earth.
"Roll intro"
Earth's mountains, in fact, are to be considered the steepest mountains of all, and practically
the only ones where it is sometimes necessary to climb sharp spires and vertical walls...
And there is a reason for this peculiarity; a reason that has to do with their origin.
On our planet, reliefs are mainly formed by the geological process of Plate Tectonics.
Basically, the Earth's crust is broken up into a dozen continental plates,
all moving like a bumper car track. If the plates collide, then the thrust causes the crust to rise
along the contact fault, with the slow emergence of huge volumes of rock. Over millions of years,
wind, water, and gravity do their work, wearing down, eroding, and sharpening
the rock to form the mountains we know today. In short, it is tectonics that, over very long
timescales, defines the formation and erosion of mountain ranges; it is tectonics that shapes some
of the characteristics of the planet's climate; and it is always tectonics that contributes to
the formation of oceans and landmasses, either favoring or slowing the development of life.
Interestingly, Earth is the only planet in the Solar System affected by this particular
phenomenon. Venus and Mars may have had something similar that moved their crusts,
but the mechanisms were different and in any case have stopped for hundreds
of millions of years, if not billions. But then, if the other planets do not
have tectonics, atmosphere, or liquid water on the surface--their mountains, how did they form?
Going very narrowly, we can say that higher or lower mountains can be formed
in at least two other ways... On the Moon, Mercury, Mars,
and other rocky bodies, most of the reliefs are what remains from the impact of comets
and asteroids capable of carving out large craters: structures with very high walls and
central peaks... But in many other cases, it was volcanism that pushed the rocks higher and higher,
accumulating over time, one eruption after another, thicker and thicker layers of lava.
All right - someone will say - but what are these mountains of other worlds? Where
are they located, and how high are they? We are getting there... but first it is
necessary to agree on the concept of "height." When we say that Everest is 8848 meters high,
we mean that this measurement was taken relative to sea level, but on other planets,
however, there are no oceans, and so it was decided that the height of those mountains,
for uniformity, is calculated relative to the plains on which they rest.
A not insignificant clarification... because by adopting this system,
the highest relief on Earth will turn out to be the volcano Mauna Kea and not Everest!
Measured above sea level, the height of Mauna Kea is in fact only 4,207 meters,
making it the 15th highest peak. But if you also consider the submerged part, then the Hawaiian
volcano in its entirety measures an impressive 9968 meters, 1 118 meters higher than Everest!
Be that as it may, you should not be surprised if you find neither Mauna Kea nor Everest in
the ranking of the highest mountains... The competition in the solar system is really fierce!
Shall we start with the Top Nine? Okay, let's get going!
In ninth place: the volcano Arsia Mons, height: 11.7 km!
Arsia Mons is the southernmost of the three volcanoes located on the Tharsis bulge on
the equator of Mars. Further north are Pavonis Mons and Ascraeus Mons,
while The Solar System's tallest volcano, Olympus Mons, lies to the northwest.
Arsia Mons, which is a monster measuring more than 400 km in diameter at its base,
is a so-called shield volcano, just like Mauna Kea. A shield volcano is a volcano usually
generated by flowing lava flows. The name comes from the shape of the volcanic cone, which, when
viewed in profile, resembles a shield. Its slope is in fact decidedly low, less than 5 percent,
so that in the near future it will certainly not be a problem to climb to the top and visit
the huge 110-kilometer-wide caldera... About two years ago, a white plume was spotted from the top
of this 50-million-year-old dormant volcano. Smoke? No, these are simply clouds that form
when water vapor-rich air is pushed up along the sides of a mountain. At high altitudes, in fact,
the lower temperature leads a fraction of the vapor to condense, forming clouds of ice crystals.
In eighth place... Euboea Montes, height: 12.5 km! More than 135 mountains have been identified on
the surface of Io, Jupiter's innermost Galilean moon. Despite the extensive volcanism still
taking place on Io, most of its mountains were formed through processes that could be loosely
described as tectonic, with large blocks of the crust being broken, shifted, raised,
or sunk by the gravitational tug-of-war that the satellite must endure due to its extreme proximity
to Jupiter. Thus, Io's mountains often appear as isolated, geometric, and skewed structures.
And this is precisely the case with Euboea Montes, in essence -- a mountain that was
formed when a slab, huge, 200 km long, was lifted and tilted about 6 degrees.
The uplift triggered massive slope failure on the northwest flank, forming one of the largest
debris aprons in the solar system. The highest peak of the entire block rises up to 12.5 km.
In seventh place... Elysium Mons, height: 12.6 km!
Another Martian shield volcano, but this time with decidedly challenging slopes,
around 20 percent. There will be some hard work before you reach the summit!
Elysium Mons is located in the volcanic province Elysium, in the Martian eastern hemisphere.
Its diameter is about 240 km, with a summit caldera about 14 km across. It is flanked by
the smaller volcanoes Hecates Tholus to the northeast, and Albor Tholus to the southeast.
In sixth place... Ionian Mons east ridge, height: 12.7 km!
This very strange mountain, like many others on Io, is also nothing more
than a large fragment of the satellite's crust crumbled by Jupiter's tidal force:
and then tossed, dragged, tilted, and abandoned like a huge Lego brick.
All in an environment as volcanic and hellish as that of the innermost of Jupiter's large moons.
Of one thing we can be sure... There will never be, even in the distant future,
a rope of explorers who will want to try their hand at conquering such a mountain...
In fifth place... Ascraeus Mons, height: 15 km! Ascraeus Mons is a large Martian shield volcano
located in the Tharsis region. It is the northernmost and highest of the three shield
volcanoes known collectively as Tharsis Montes. It has a diameter at the base of about 480 km
and is the second-highest mountain on Mars. The volcano has a very low profile with an
average slope of 7°. The slopes are steeper in the central part of the flanks, flattening
toward the base and near the summit, where there is a broad summit plateau and a caldera complex.
In fourth place... Boosaule Montes, height: 17.5 km!
Boosaule Montes is the highest mountain in Io, located northwest of Pele (an active volcano
recognizable in images released by probes by the conspicuous ring of red sulfides surrounding it).
With a height of about 17,500, Boosaule turns out to be higher
than Everest and K2 stacked on top of each other!
It holds the important title of the highest non-volcanic mountain in the solar system.
In third place... the Equatorial ridge of Japetus, height: 20 km!
Japetus, with a diameter of 1,469 km, is the third largest moon of Saturn and
the 11th largest in the solar system. It is a relatively low-density object,
consisting mainly of ice, and hosts several distinctive and unusual features,
such as a noticeable difference in brightness between its hemispheres,
as especially the massive equatorial ridge that runs three-quarters around the moon.
There is nothing like it in our solar system-it is something never seen before. Looking at photos
of Japetus, one has the feeling of looking at a walnut, with the two halves of the
shell joined by the classic raised edge... The incredible structure stretches along the
equator for about 1,300 km, resembling a mountain range 25 km wide and 13 km high on average, with
peaks rising more than 20 km above the surrounding plains. It is still unclear how such an oddity was
formed--there is no shortage of hypotheses, but none of which can explain all of its features.
In second place... Olympus Mons, height: 21.9 km! And this one is a real surprise... Tell the truth,
didn't you also expect this massive volcanic formation to be confirmed,
as it has been doing for decades, as the highest in the entire solar system?
But no, this time (but now, forever), Olympus Mons will have to settle for the podium...
This Martian volcano, which stands along with three others in the Tharsis region,
is nevertheless a true geological monstrosity... It is the result of many thousands of highly fluid
basaltic lava flows that poured from volcanic vents over a long time. And
its base, more than 600 km in diameter, encloses an area the size of Arizona...
Being a shield volcano, Olympus Mons has a very gently sloping profile. The average slope on
the flanks of the volcano is only 5 percent. The slopes are steeper near the central part of the
flanks and become shallower toward the base, giving the flanks an upward concave profile.
The extraordinary size is probably due to the fact that Mars, unlike Earth,
has no tectonic plates. Because of this, the crust remains fixed and the hot spot that
feeds it has continued to produce lava for millions of years, always in the same spot.
Also truly spectacular is the escarpment that bounds the perimeter of the base,
with sheer walls from 3,000 to 8,000 meters high… with the whole
thing resembling an impregnable fortress. The first human explorers who would like
to try to climb the imposing volcano will have to struggle hard to find a viable access route!
In first place... Rheasilvia central peak, height: 25 km!
Still, until 2011, there was no doubt that Olympus Mons was the highest mountain in the solar system.
Then, in that year, the visit that the Dawn probe made to the asteroid Vesta, an object
525 km in diameter, suddenly changed the game... Indeed, the probe was able to detect the physical
characteristics of a huge impact crater--a surface depression so large (505 km) that it affected
practically an entire hemisphere of the asteroid! And the extraordinary scar was given the name
Rheasilvia, from Rhea Silvia, the mythological vestal virgin mother of the founders of Rome.
But there was more... in the center of the crater rose a mountain that
on balance turned out to be more or less 25 km high than the sands of the seabed!
In short... In the end, the tallest mountain was found on the smallest of the celestial
bodies considered so far! Isn't this magnificent?