Interplanetary Experience
Interplanetary Experience
[Caption above the panel:] Where to go on Earth to get the Interplanetary Explorer Experience
[A chart with seven rows with celestial bodies on the left side of seven lines and a description on the right side. The first entry has three celestial bodies in two rows, the rest are in one row, although the last entry encompasses a list of planets. Four times the day/night side of the celestial bodies is mentioned in brackets.]
Pluto, Moon (night) Mt. Everest at night Mercury (night) Moon (day) Mt. Everest at noon under a tanning lamp Mercury (day) A lava flow on a volcano at noon Venus A heat-shrink wetsuit in a blast furnace Mars Mt. Everest at sunset Titan Waist-deep in an outgassing Siberian swamp Jupiter-Neptune Jumping from a high-altitude balloon over an Antarctic Ocean winter storm

This comic lists ten celestial bodies : most other planets , the dwarf planet Pluto , as well as two moons , the Earth's Moon and Titan (the largest moon of Saturn ). It then asks what places on Earth people could go to for a real Interplanetary Experience , as if they were explorers on these planets. It turns out that none of these ten other worlds are very nice to visit...
This is a parody on organizations that in preparation for future planetary exploration organize half-realistic experiments in human behavior on other planets, trying to emulate or mock-up - often on low budget - the conditions in which future explorers are to live and work. For this purpose, they build mock-up bases, habitats etc. in places that look like other planets or have the environmental conditions somewhat similar to other celestial bodies' surfaces. They seek out desolate places like deserts or polar regions for this purpose.
In this comic Randall tries to identify places on Earth that actually have environmental conditions as close to these other worlds' as can be possible on the surface of the Earth. Some of the places suggested by Randall are borderline-survivable for a human, but most will kill you extremely quickly without a lot of high-tech gear - whether through severe hypothermia (freezing), conflagration (fire), crushing (high pressure), or from violent winds.
Basically, nowhere in the solar system , except Earth, is even close to survivable (and there is actually only a very limited amount of Earth's surface where humans can actually live permanently). There is no planet or moon with a breathable atmosphere, or where the temperature stays within the human-tolerable range of roughly −20°C to 40°C (−5°F to 105°F, 250-310 K). It is also only with really good clothing and a place to stay at night that humans can live in a place much colder than 10°C for longer periods. The only place humans have so far ventured off-Earth is the Moon, and only during lunar morning while wearing thick pressurized spacesuits.
Some celestial bodies, like Venus and Jupiter , may never be visitable by humans without either huge advances in material science or full-scale terraforming (for Venus). Some places, like the centers of any planet (for example, the gas giants or even Earth itself), will probably never be visited, even by robots. (The title text suggests what happens when falling towards the center of a gas giant).
Below is a list going through the seven suggested places on Earth. Due to the low pressure and temperature on the top of Mount Everest it is mentioned no less than three times, but using different time of day to represent different celestial bodies. In the first entry it even takes care of three in one go. Two of those are the Moon and Mercury, but for both only on their night side facing away from the sun. They are thus each mentioned twice, as there is a huge difference in environmental conditions between the sunlit faces of these two and their night sides. On the other end of the temperature scale are mentions of lava and a blast furnace ; also high pressure environments are suggested to simulate other planets. The last goes for the gas giants, which are all mentioned together in the last entry.
The two groupings explains why there are only seven places mentioned for ten celestial bodies. The reason that the Moon is mentioned is of course that it is the closest companion to Earth and that we have actually visited it. That the only other moon mentioned is likely because it is the only really cold celestial body that actually has an atmosphere as well as a surface humans could stand on. But there are many other large moons that would be interesting to visit, like the Galilean moons especially Europa . But that could probably be compared to being on Pluto, except the sun is a bit larger. That Pluto is included as the only dwarf planet is probably because it was still a planet when Randall was a kid (see 473: Still Raw ) and is the most recent (new) celestial body visited by a space probe at the time of release of this comic. This was celebrated by Randall in 1551: Pluto .
The title text is just a continuation of the last entry about falling down through the atmosphere of a gas giant, and it is also explained in the table below. This was also explored in What If? Jupiter Submarine .
The dwarf planet Pluto is a small icy rock so far away from the Sun that it practically makes no difference if it is day or night, the Sun is just the brightest star in the sky of Pluto's "day" side. But for both the Earth's Moon and Mercury (the innermost and smallest planet of the solar system ) it makes a huge difference, which is why there is both a day and a night experience mentioned for these two celestial bodies (see below). Although they are very much closer to the Sun than Pluto, this makes no difference during their night time (when they face away from Sun). They are both relatively small, rocky bodies with practically no atmosphere and relatively slow rotation. Therefore their surfaces not illuminated by the Sun will cool down to very low temperatures (around -170 °C, -290 °F, 100 K), making their nighttime hemispheres desolate, dark and cold places. Randall proposes the summit of Mount Everest (the tallest mountain on Earth) as the place that will emulate the conditions most closely. It is a rocky, desolate and cold place. Even though it is not the coldest place on Earth, it is the highest point on land, therefore it has the lowest atmospheric pressure. It cannot be compared to the near-zero pressure and 100 Kelvins conditions on the aforementioned bodies, but it is as close as you can get on Earth. The top of Mt. Everest has an air pressure just 1/3 of what it is at sea level, and the oxygen levels are so low that they are barely survivable, although a few people have reached the top without oxygen tanks , but others have died after losing their oxygen supply, making it as close as you can get on Earth to the near-vacuum found on these worlds.
As explained above, Mount Everest is as good an emulation of the Moon surface at night as you can get on Earth. During the Moon's day, its surface gets about as much solar radiation as Earth at noon, because both bodies' distance from the Sun is almost the same. The Earth's atmosphere, however, stops most of the Sun's ultraviolet radiation . A tanning lamp is a device emitting mostly ultraviolet radiation for the purpose of artificial tanning ; here it is used to augment the filtered Sun's radiation in an attempt to emulate the Moon's daytime conditions better. Since the Moon does not have any atmosphere it is hard to discuss the temperature experienced on the Moon, but still the surface of the Moon reaches temperatures above water's boiling point (100°C or 212 °F) during the day with an average daytime temperature of the Moon at 107°C (224.6 °F). This effect will not be very well emulated on top of Mount Everest or even in the hottest (non-volcanic) place on Earth's surface that reaches 53.9°C (129°F) — see the what if? Flood Death Valley .
Mercury's surface never quite reaches lava temperatures (if it did, it would be molten), but it gets close. At noon, Mercury's equator reaches 420°C (800°F, 700 K). Lava is a liquid usually at temperatures from 700 to 1,200 °C (1,300 to 2,200 °F, 970 K to 1470 K) but depending on what type of rock it's formed from, lava can erupt at temperatures as low as 500°C-600°C (930°F-1100°F, 770–870 K). Standing on a volcano on a partially solidified lava flow (which, it goes without saying, is incredibly dangerous) would expose you to similar temperatures.
Near the poles, Mercury's surface temperature is always very low as the axial tilt is almost zero, meaning that the poles do not get much direct sunlight and their temperature is constantly below −93 °C (−136 °F, 180 K).
The average surface temperature on Venus is around 470°C (870°F, 740 K) (enough to melt lead at 327 °C (620°F, 600 K), which is the usual comparison ), and the pressure is 92 bar (by comparison, pressure on earth is only about 1 bar). A blast furnace is a bit too hot — the blast itself is 900 °C to 1300 °C (1600 °F to 2300 °F, 1170 K to 1570 K), and they can reach 2000 °C — but either temperature is enough to kill you in seconds. As the blast furnace would emulate Venus' temperature but not pressure, Randall proposes that a daring volunteer wear a hypothetical heat-shrink wetsuit. A wetsuit is an elastic garment worn mostly over the whole body by swimmers, divers etc. Heat-shrink tubing is an elastic tube made of a material that shrinks when heated, used to provide extra insulation and mechanical or environmental protection in electrical and electronics work — you put a length of tubing over your wire, connector, or a joint and heat it with a hot air gun, making it shrink and crimp over your device. A hypothetical heat-shrink wetsuit worn while sitting in a blast furnace supposedly would shrink rapidly in the extreme temperature, exerting great pressure on your body, thus emulating Venus' surface atmospheric pressure. In other words, do not go to Venus!
Again use Mount Everest's thin atmosphere and very cold temperatures to emulate the planet, but Mars' dusty, greenhouse-gas-containing atmosphere means it's not as cold as Mercury at night, nor as hot as the Moon during the day. Also the sun is much farther from Mars than from the Earth/Moon system, but much, much closer than Pluto, so it should be colder than the day side of the Moon. But the Sun still looks like a sun rather than a star from Mars, unlike on Pluto. The sunset will also make the sky reddish-purple, similar to the way the Martian sky often looks .
Titan, the largest of Saturn moons (and one of the largest moons in the solar system) is one of the promising worlds for life.  Given that its surface temperature is −180°C (−290°F, 95 K), that says a lot about how inhospitable the rest of the solar system is. The chemistry of the planet is interesting — there are lots of nitrogen compounds and hydrocarbons and the atmosphere is mostly nitrogen and methane. It has been confirmed that methane lakes exist on Titan's surface. It thus follows that there is likely also some precipitation of methane "snow", similarly to how water forms lakes and falls down as sleet on Earth. Similar compounds are produced by rotting material in swamps , hence the comparison to a cold Siberian swamp. Due to the global warming large area of the tundra in Siberia that used to be permanently locked in permafrost are now heating up enough to release these gases . It might thus be possible to end up waist deep in one of these "heated" swamp areas due to the resulting outgassing . Sadly for the global temperature this outgassing just increases the release of greenhouse gasses, making the global warming increase even faster. This may very well be the reason Randall chooses to mention it here, as another call back to recurring theme of Climate change and to the recent comic 1732: Earth Temperature Timeline . One key difference though is that on Earth, swamps are mostly water. On Titan — if they exist at all — they're liquid methane. Siberia also has some of the most extreme temperature differences on Earth, while Titan is just consistently cold. The coldest place in Siberia is the Pole of Cold , the coldest point in the Northern hemisphere having reached −71.2 °C (−96.2 °F, 202 K). Not quite Titan levels of cold, but certainly deadly enough. But in such cold places there would be no outgassing, so on Earth it is not possible to have both the cold and the outgassing.
Note that it is Jupiter to Neptune thus including also Saturn and Uranus . They are under one called gas giants for a reason. All the planets are very cold and have stormy weather (Uranus is the least active, and Neptune is the most active) and extreme temperature and pressure gradients.  On the edge of the atmosphere, conditions aren't much different from space, but as you fall in, the temperature and pressure rapidly increase past the freezing point (allowing clouds of ice and water). This environment is simulated by jumping out of a high-altitude balloon (low pressure and cold) and falling down into an Antarctic Ocean winter storm, a very cold and violently windy place. The storms on the gas planets can be much more violent than any storm on Earth. On Neptune the storms can reach 2,100 km/h (580 m/s, 1,300 mph), whereas the Great Red Spot of Jupiter only reaches 430 km/h (120 m/s, 270 mph). The highest wind speed on Earth (outside tornadoes ) has been measured at 408 km/h (113 m/s, 253 mph), and that was only the gusts.
The title text continues the last entry in the main comic, so this explanation is also a direct continuation of the above entry. The extreme temperature and pressure gradients mentioned do not stop when the atmospheric temperature and pressure increase beyond water's freezing point.  Soon the temperature reaches past the boiling point, and on up to thousands of degrees and unimaginably high pressures, increasing further until reaching the central core. The cores of Neptune and Uranus most likely consist of rock (superheated silicates, iron and nickel) or in the case of Saturn and Jupiter of liquid metallic hydrogen , where the extreme high-pressure and temperature causes hydrogen to behave like a metal. The suggested simulation of this environment is to fall into a super hot bath tub that falls into the burning engine room of a ship that is sinking, and thus is about be crushed by the water pressure of the deep ocean.  This is the closest representation of the pressure and temperature conditions of the inner parts of the gas giants that can be imagined on Earth, but of course the cores of these planets are far, far more inhospitable than the scenarios mentioned above. Descending into Jupiter was also explored in the what if? Jupiter Submarine .
[Caption above the panel:] Where to go on Earth to get the Interplanetary Explorer Experience
[A chart with seven rows with celestial bodies on the left side of seven lines and a description on the right side. The first entry has three celestial bodies in two rows, the rest are in one row, although the last entry encompasses a list of planets. Four times the day/night side of the celestial bodies is mentioned in brackets.]
Pluto, Moon (night) Mt. Everest at night Mercury (night) Moon (day) Mt. Everest at noon under a tanning lamp Mercury (day) A lava flow on a volcano at noon Venus A heat-shrink wetsuit in a blast furnace Mars Mt. Everest at sunset Titan Waist-deep in an outgassing Siberian swamp Jupiter-Neptune Jumping from a high-altitude balloon over an Antarctic Ocean winter storm
