The solar system is a vast and diverse place, with many different celestial bodies that have varying temperatures. Some of these temperatures are so extreme that they are hard to imagine.
For example, the sun's surface temperature is about 5800 K (5500 °C or 9900 °F), while its core temperature is about 15.7 million K (15.7 million °C or 28.3 million °F) . On the other hand, some places in the solar system are so cold that they are barely above absolute zero, the point at which molecular motion stops.
But what is the coldest place in the solar system? And how does it compare with the coldest place on Earth? In this article, we will explore these questions and learn some fascinating facts about the extreme coldness of space.
The Coldest Place on Earth
Before we look at the coldest place in the solar system, let's first see what is the coldest place on Earth. According to the World Meteorological Organization (WMO), the lowest temperature ever recorded on Earth was -89.2 °C (-128.6 °F) at Vostok Station, Antarctica, on July 21, 1983 . This temperature was measured by a ground-based thermometer and verified by satellite data.
However, there may be even colder places on Earth that have not been measured yet. In 2013, a NASA study using satellite data found that several spots on a high ridge in East Antarctica had temperatures as low as -93.2 °C (-135.8 °F) between 2004 and 2016 . These spots are located near Dome A, the highest point on the Antarctic ice sheet, and are likely to be colder than Vostok Station because they are higher and more isolated from warmer air masses.
The Coldest Place in the Solar System
Now that we know what is the coldest place on Earth, let's see what is the coldest place in the solar system. There are many factors that affect the temperature of a celestial body, such as its distance from the sun, its albedo (reflectivity), its atmosphere (or lack thereof), its rotation and tilt, and its internal heat sources. Therefore, it is not easy to compare temperatures across different planets, moons, asteroids, comets and other objects.
However, based on current data and estimates, there is some consensus among scientists that the coldest place in the solar system is located on our nearest celestial neighbor: the moon. More specifically, it is a crater near the lunar south pole called Hermite.
Hermite: The Coldest Crater
Hermite is a lunar impact crater that is about 109 km (68 miles) in diameter and located along the northern lunar limb, close to the north pole of the moon . It was named after Charles Hermite, a French mathematician who studied elliptic functions and number theory .
Hermite is a worn and eroded crater with a rugged outer rim that has been notched and incised by past impacts . Its interior floor has been resurfaced by lava flows or ejecta from nearby impacts, forming a wide plain that is pock-marked by numerous tiny craters and low hills . There is also a small crater on the floor near the northeastern wall.
But what makes Hermite special is that it has one of the largest permanently shadowed regions (PSRs) on the moon . PSRs are areas that never receive direct sunlight because they are located in deep craters or on slopes that face away from the sun . Because of this, PSRs are extremely cold and dark places that can preserve water ice and other volatile substances for billions of years .
In 2009, NASA's Lunar Reconnaissance Orbiter (LRO) discovered that Hermite's southwestern edge is **the coldest place recorded in the solar system**, with temperatures as low as **26 K (-413 °F or -247 °C)** ³⁴. This temperature was measured by LRO's Diviner instrument, which detects infrared radiation emitted from surfaces .
For comparison, Pluto's surface only gets down to about **43 K (-382 °F or -229 °C)** when it is closest to the sun ⁴ . Pluto is much farther from the sun than the moon (about 40 times on average), but it has a thin atmosphere that helps retain some heat and an albedo of about 0.6 that reflects some sunlight . The moon has no atmosphere and an albedo of about 0.12 , which means it absorbs more heat but also radiates it more quickly.
Hermite's temperature of 26 K is also lower than any other known PSR on the moon or Mercury (the closest planet to the sun), which have temperatures ranging from about 30 K to 70 K (-406 °F to -333 °F or -243 °C to -203 °C) . Hermite's PSR is so cold because it is not only shielded from direct solar illumination but also from secondary heating sources such as reflected sunlight or thermal radiation from nearby warm surfaces ⁴ . This makes it a "doubly shadowed" crater that can only receive heat from cosmic rays or micrometeorites ⁴.
Possible Water Ice Presence
Because of its extreme coldness and darkness, Hermite's PSR may also harbor a large amount of water ice within its surface or subsurface layers. Water ice is one of the most abundant and important substances in the solar system because it can provide resources for future exploration missions or even support life forms.
There are several lines of evidence that suggest water ice may exist in Hermite's PSR. One of them is based on radar measurements by NASA's Mini-RF instrument aboard LRO and India's Chandrayaan-1 orbiter [19][20]. Radar waves can penetrate into surfaces and reflect back depending on their composition and structure. Surfaces with water ice tend to have high circular polarization ratios (CPRs), which indicate how much of the reflected radar waves have changed their polarization direction.
Hermite's PSR has one of the highest CPRs among all lunar PSRs measured by radar instruments, suggesting that it contains a significant amount of water ice within its upper few meters [19][20]. However, CPRs can also be affected by other factors such as surface roughness or rockiness, so they are not conclusive indicators of water ice presence.
Another line of evidence comes from spectral measurements by NASA's Moon Mineralogy Mapper (M3) instrument aboard Chandrayaan-1 [21][22]. Spectral data can reveal information about surface composition by analyzing how different wavelengths of light are absorbed or reflected by different materials. Surfaces with water ice tend to have characteristic absorption features at certain wavelengths in the infrared range.
Hermite's PSR has some spectral signatures that are consistent with water ice presence at certain locations within its boundary [21][22]. However, these signatures are weak and noisy due to low signal-to-noise ratio caused by low illumination levels and thermal emission interference. Therefore, they are also not definitive indicators of water ice presence.
A third line of evidence comes from thermal measurements by LRO's Diviner instrument [23][24]. Thermal data can provide information about surface properties such as temperature, thermal inertia and albedo. Surfaces with water ice tend to have low temperatures, high thermal inertia and high albedo compared to surfaces without water ice.
Hermite's PSR has some thermal characteristics that are compatible with water ice presence at certain locations within its boundary [23][24]. However, these characteristics are also influenced by other factors such as surface roughness or rockiness,
so they are also not conclusive indicators of water ice presence.
Therefore, while there are multiple lines of evidence that suggest water ice may exist in Hermite's PSR,
none of them are definitive enough to confirm its presence or abundance.
More detailed measurements and analyses are needed to determine if water ice exists in Hermite's PSR and how much of it there is.
Conclusion
In this article, we have learned that the coldest place in the solar system is likely to be a crater near the lunar south pole called Hermite, which has temperatures as low as 26 K (-413 °F or -247 °C). This temperature is lower than any other known place in the solar system, including Pluto, Mercury or other lunar craters.
Hermite’s extreme coldness is due to its location in a doubly shadowed region that receives no direct or indirect sunlight or thermal radiation. Hermite’s coldness also makes it a potential reservoir of water ice, which could provide resources for future exploration missions or even support life forms.
However, the presence and abundance of water ice in Hermite’s region are still uncertain, and require more detailed measurements and analyses to confirm.
We hope you enjoyed this article and learned something new about the coldest place in the solar system.
Source:
(2) https://www.newscientist.com/article/dn17810-moon-is-coldest-known-place-in-the-solar-system/.
(3) https://www.guinnessworldrecords.com/world-records/600839-coldest-planet-in-the-solar-system.
(4) https://www.livescience.com/coldest-place-in-solar-system.
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