Mohawk Valley Astronomical Society

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Frigid Inferno

by Perry Pezzolanella

We live in a world of temperature extremes. We are no strangers to extremes here in Upstate New York where the seasons are clearly defined. From broiling heatwaves approaching 100ºF to shivering cold waves as low as -30ºF, it is amazing how dramatic the seasons change here. Extreme temperatures also occur on other worlds in the Solar System with some extremes more intense and varied than can be imagined.

Earth is often called the “Goldilocks Planet” that is just right for life, neither too hot nor too cold overall. That is a correct assumption as long as one does not decide to live at one of the poles or in a desert. The highest direct measurement with a thermometer is 134.0ºF at Furnace Creek Ranch in California’s Death Valley on July 10, 1913. The coldest ever is -128.6ºF at the Vostok Station in the Antarctica on July 21, 1983. Infrared sensors from satellites have found conditions even more hostile where thermometers are not present for direct recording. It can get as hot as 158.0ºF in the Lut Desert in Iran and as cold as -135.8ºF on a high plateau in Antarctica not far from the Vostok Station. These extremes are not recognized as official world records due to absence of instruments at these locations but satellites have highly calibrated infrared sensors, which are accurate. According to satellite data it is possible to get as cold as -140ºF and as hot as 160ºF, which makes a 300ºF range of extremes for Earth. This boggles the mind and trying to survive in these extremes is almost certain to be deadly.

All of the worlds in our Solar System have had their temperatures measured by spacecraft that either flew by or went into orbit around them. The spacecraft all bristle with sensors and equipment that carefully and accurately measure the temperature and environment of these worlds. The instruments are highly calibrated so that there are no erroneous readings to leave any doubt in the minds of the scientists involved, but if it is mandatory to have an instrument on the surface to take a direct reading to make it official, then there are several worlds that have official temperatures. This elite club includes Venus, the Moon, Mars, and Titan.

The series of Soviet Venera and Vega spacecraft have successfully landed and measured the surface temperature on Venus at nearly a dozen locations so it can officially be said that the average surface temperature is truly a blistering 870ºF. The probes that landed at higher elevations have measured it as cool as 840ºF and the few that have landed in the lowland plains have recorded as hot as 905ºF, a true inferno with no reason to question. Titan is at the other extreme as it orbits Saturn nearly a billion miles from the Sun. A small probe called Huygens landed on Titan in January 2005 and officially confirmed a frigid surface temperature of -290ºF, which supported the same readings from the two Voyager spacecraft that flew past it decades earlier. The feeble sunlight is hardly any brighter than a moonlit night on Earth and does little to warm Titan. It is the thick nitrogen/methane atmosphere that is 1.6 times as thick as Earth that helps keeps it about 20-30 degrees warmer than it would be otherwise.

Mars has been invaded by several spacecraft that have landed and roved its surface all carrying sensors to directly measure the surface temperature. Overall it is as nasty as Antarctica with an average temperature of -64ºF. Daytime highs can reach 50ºF but that is within a few feet of the ground. Only a few feet further up it is freezing cold. It is possible to have warm feet and a frozen head on Mars at the same time! This is due to the very thin atmosphere that is 100 times thinner than Earth and cannot readily retain heat. The rovers have recorded it as cold as -144ºF during the long winter nights and orbiters have indirectly measured the ice caps as cold as -190ºF. Several sensors have been placed on the Moon through the decades and it is also a world of extremes that is due to the lack of an atmosphere. It may grow as hot as 253ºF during the 2-week long day, but the 2-week long night is as cold as -243ºF, nearly a 500ºF spread!

Everywhere else we have to rely on remote sensing from spacecraft. Mercury has the most extreme range of temperature of all at 1100ºF with it as hot as 800ºF during the long day and as cold as -300º during the long frigid nights. This is also due to the lack of an appreciable atmosphere. The Outer Solar System is savagely cold and gets worse the farther away from the Sun as expected. The moons all have icy surfaces to a varying degree and the type of ice is dictated mainly by the distance from the Sun. In the realm of Jupiter and Saturn the ice is mainly water and ammonia. Methane ice shows up out near Uranus and nitrogen ice forms out near Neptune. There is even carbon monoxide ice at Pluto. The moons of Jupiter are as cold as -250ºF, Saturn’s moons chill to -300ºF, the moons of Uranus are as cold as -350ºF, and Neptune’s moons are at nearly -400ºF with Triton being accurately measured at -392ºF when Voyager 2 flew past it during August 1989, making it the coldest world known.

Pluto has it even worse even though it is a little warmer at -380ºF due to an appreciable atmosphere as detected from earthbound observations. It is on a highly elongated orbit that takes it as far away as 4.6 billion miles from the Sun. At that distance most, but not all, of the atmosphere freezes out onto the surface and Pluto can chill as low as an estimated -420ºF at the poles where the Sun may not shine for over a century due to its extreme 120º axial tilt. New Horizons detected a frigid -391ºF on the surface at the vast icy plain of Sputnik Planum when it flew by July 14 last year.

Temperature is all relevant because anyone living on Venus would think that most of the rest of the Solar System is cool to downright frigid while anyone living on Pluto would think anywhere else is balmy or a downright inferno. It is indeed amazing how lucky we are to be at just the right distance from the Sun on just the proper size planet to hold onto an atmosphere just thick enough and with just the right ingredients to keep us from becoming a frigid ice ball or a global inferno.