APOD: Earthset from the Lunar Orbiter... (2016 Jan 04)

[neufer]

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Coldest Spot on the Moon

<<Hermite is foreground for an Earthrise in 2007, witnessed by Japan's Kaguya. Hugging the west side of the Moon's north polar region Hermite is within the Zone of Librations. Though two-thirds of its 114 km-wide interior is technically on the Moon's Far Side it can still be seen from Earth. Not along its southwestern interior, however, in perpetual shadow and where LRO's Diviner has measured the Moon's coldest surface temperatures, temperatures as cold as any now known this side of the Kuiper Belt [JAXA/NHK/SELENE].>>

[b][color=#0000FF][size=125]Dark Hermite crater just to the left of the lunar north pole[/size][/color][/b]

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<<Hermite is a lunar impact crater located along the northern lunar limb, close to the north pole of the Moon. It was first discovered in 1964. To the west is the crater Rozhdestvenskiy, and to the south are Lovelace and Sylvester. From the Earth this crater is viewed nearly from the side, and it is illuminated by oblique sunlight. This is a worn, eroded crater with a rugged outer rim that is notched and incised from past impacts. A crater overlies the southwestern rim, and the two formations have merged to share a common interior floor. A pair of small craters lies along the southern part of the rim, and a small crater is also attached near the northern end. The interior floor has been resurfaced, so that it forms a wide plain that is pock-marked by numerous tiny craterlets and low hills. There is a small crater on the floor near the northeastern wall.

In 2009, it was discovered by NASA's Lunar Reconnaissance Orbiter that Hermite is the coldest place recorded in the solar system, with temperatures at 26 K. For comparison, Pluto's surface only gets down to about 43 K.>>

[Nitpicker]

My question would be: what are rough elevations above the lunar surface that the respective hills in the foreground rise? And the elevation of the farthest most peak in this frame??

It is all lunar surface. The larger crater floors and mares tend to be below the Moon's current average/reference/datum elevation of (I think) 1737.4 km (above the centre of the Moon). I estimate that the highest point on the lunar surface that we see in the APOD is roughly 4 km higher than the floor of the crater (Compton) in the foreground. The mountains in the foreground, within the western part of Compton, probably rise less than 1 km above the floor.

Source: http://target.lroc.asu.edu/q3/

[Ironwood]

This is a telescopic view. If one were on the moon with just the naked eye, the Earth would be approximately the size of a quarter held 30 inches away from the eye. Near the horizon it would appear larger due to the famous Earth Illusion.

[DavidLeodis]

The application for astronaut selection that was brought up through the "future astronauts" link was interesting. Sadly I fail to qualify on several grounds, though my likely also being stiff does not seem to be listed!

[Ann]

The application for astronaut selection that was brought up through the "future astronauts" link was interesting. Sadly I fail to qualify on several grounds, though my likely also being stiff does not seem to be listed!

That makes two of us, David!

Although I'd surely love, love, love to see our dear old Earth soar in the sky as seen from the Moon. (Of course I'd also love to see how blue or non-blue it really is!)

Ann

[tomatoherd]

an easy question for someone: from the lunar surface, what is the angular size of Earth in its view? If the moon is ~1/2 degree in ours, what are we in its?

[tomatoherd]

Art: WHY is the coldest spot in the solar system on the moon? what contributes to that phenomenon??

[Chris Peterson]

Art: WHY is the coldest spot in the solar system on the moon? what contributes to that phenomenon??

It's not the coldest spot in the Solar System. It's typical of any place well shielded from the Sun and sources of radiant or convective heat.

[Nitpicker]

an easy question for someone: from the lunar surface, what is the angular size of Earth in its view? If the moon is ~1/2 degree in ours, what are we in its?

Earth radius = 6371 km
Moon radius = 1737 km

So, angular size of Earth from Moon is about 0.5 degrees times 6371/1737, or 1.8 degrees, or a little smaller than the width of one's outstretched thumb.

[neufer]

Art: WHY is the coldest spot in the solar system on the moon? what contributes to that phenomenon??

It's not the coldest spot in the Solar System. It's typical of any place well shielded from the Sun and sources of radiant or convective heat. It's typical of any place well shielded from the Sun and sources of radiant or convective heat.

Hermite crater is the coldest recorded place in the solar system.

All small solar system objects further than 100 AU should be colder than 25 K.

[Nitpicker]

Haven't we created colder temperatures in laboratories on Earth? So, the eternally dark bit of Hermite is merely the coldest recorded (by humans) natural place in the solar system.

[Chris Peterson]

Haven't we created colder temperatures in laboratories on Earth? So, the eternally dark bit of Hermite is merely the coldest recorded (by humans) natural place in the solar system.

Certainly, it is common in the lab to have temperatures of just a few millikelvins. Liquid helium is colder than 4K. And in the realm of bizarre physics, temperatures below absolute zero have been measured.

[Ann]

Haven't we created colder temperatures in laboratories on Earth? So, the eternally dark bit of Hermite is merely the coldest recorded (by humans) natural place in the solar system.

Certainly, it is common in the lab to have temperatures of just a few millikelvins. Liquid helium is colder than 4K. And in the realm of bizarre physics, temperatures below absolute zero have been measured.

Click to view full size image

Bizarro. Source: http://comicsalliance.com/bizarro-back- ... nkenstein/

I'm not absolutely sure I want you to elaborate on that, Chris. It sounds Bizarre to me.

Ann

[Nitpicker]

Negative temperatures are not 0 K. (Groan.)

https://en.wikipedia.org/wiki/Negative_temperature

A system with a truly negative temperature on the Kelvin scale is hotter than any system with a positive temperature. If a negative-temperature system and a positive-temperature system come in contact, heat will flow from the negative- to the positive-temperature system.

[Beyond]

Negative to positive, just like the inside of a battery, only batteries aren't hot and cooler. At least none that i know of.

[Nitpicker]

No, not like a battery at all. Batteries aren't so bizarre.

[Beyond]

They start getting low on water, they can be at least somewhat bizarre, especially when they're connected to a trickle charger for a long time.
On the outside, where it can be seen, the batteries flow is from positive to negative. On the inside, it's from negative to positive. So there is two directions of flow to a battery. One seen and one unseen. Do the positive and negative temperatures you're speaking of have seen and unseen flows to them?

[MarkBour]

Hermite crater is the coldest recorded place in the solar system.
All small solar system objects further than 100 AU should be colder than 25 K.

If it's not redundant, then I'll predict that the Moon's polar spots will not hold this record for very long. It's not fair. We've tracked down the coldest spot on the Moon. Soon enough, a probe in some place will beat it. Perhaps New Horizons, when it visits 2014 MU69. Perhaps some measurement out in the asteroid belt. All you'd need is an object with a suitable rotational motion to keep part of it in perpetual darkness.

... perhaps Leonardo DiCaprio, if he doesn't get nominated for the Revenant.

[neufer]

Hermite crater is the coldest recorded place in the solar system.
All small solar system objects further than 100 AU should be colder than 25 K.

If it's not redundant, then I'll predict that the Moon's polar spots will not hold this record for very long. It's not fair. We've tracked down the coldest spot on the Moon. Soon enough, a probe in some place will beat it. Perhaps New Horizons, when it visits 2014 MU69. Perhaps some measurement out in the asteroid belt. All you'd need is an object with a suitable rotational motion to keep part of it in perpetual darkness.

... perhaps Leonardo DiCaprio, if he doesn't get nominated for the Revenant.

It's not fair but I'll predict that the Moon's polar spots will hold the title: "coldest recorded place in the solar system" for a long while.

New Horizons has no infrared thermal measurement capability so we won't know how cold the polar night got on Pluto or Charon much less how cold 2014 MU69 will be.

The Lunar Reconnaissance Orbiter is perhaps unique as an "interplanetary" space probe with very long wavelength [50 - 200 μm] infrared thermal measurement capability. Even the Mars Reconnaissance Orbiter Mars Climate Sounder (MCS) is only capable of infrared thermal measurements down to 50 μm [i.e., greater than ~60K].

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<<Diviner is an infrared sensing instrument aboard NASA's Lunar Reconnaissance Orbiter, part of the Lunar Precursor Robotic Program which is studying the moon. It is also referred to as the DLRE, for 'Diviner Lunar Radiometer Experiment' - A radiometer is a sensor designed to measure Electromagnetic Radiation, especially infrared heat radiation.

Diviner is a nine channel infrared filter radiometer based on the design of the Mars Reconnaissance Orbiter Mars Climate Sounder (MCS). The four broad thermal channels are intended to characterize the surface thermal emission over a wide range of temperatures, as well as the presence of anisothermal emission due to the presence of slopes, shadows and rocks with Diviner's field of view. In channels B2 [50 - 100 μm] and B3 [100 - 200 μm], Diviner's minimum detectable temperature is less than 30K. Diviner's mineralogy channels should allow confident determination of the wavelength peak of the Christiensen feature at temperatures above 300K.>>

[Chris Peterson]

It's not fair but I'll predict that the Moon's polar spots will hold the title: "coldest recorded place in the solar system" for a long while.

New Horizons has no infrared thermal measurement capability so we won't know how cold the polar night got on Pluto or Charon much less how cold 2014 MU69 will be.

Well, maybe. And it depends on how you define "record". Direct IR measurements aren't the only way to measure temperature. The presence of elements or compounds in certain forms can serve as a proxy for temperature, and those are things that can be detected by other spacecraft, or even from the Earth or Earth orbit.

So, we'll see.