[HN Gopher] Blue Ghost lander captures sunset shots on moon befo...
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Blue Ghost lander captures sunset shots on moon before falling
silent
Author : pseudolus
Score : 92 points
Date : 2025-03-19 10:45 UTC (4 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| perihelions wrote:
| Here's the other photos of Earth eclipses seen from the moon,
|
| https://fosstodon.org/@AkaSci/114163135356046535
| celeritascelery wrote:
| I am curious what causes these landers to fail in the bitter cold
| of night? Is it the batteries? It seems like circuitry should be
| fine.
| looperhacks wrote:
| The moon gets _really_ cold, way below spec for most
| electronics. That's why sensitive parts are sometimes in a
| heating component, but that also depends on the battery. And
| yes, cold batteries might not recover properly.
| celeritascelery wrote:
| Is it the actual silicon that can't handle it, or is
| contraction in joints and connections that breaks?
| atkailash wrote:
| Meanwhile voyager is beyond the solar system. I don't see why
| they didn't use something that's not solar so they aren't
| just littering the moon
| amenghra wrote:
| The moon is huge compared to a single thing we can
| currently send there. Comparatively, we are "littering" our
| own atmosphere a ton more during liftoff.
| alwa wrote:
| I can't help but suspect Starship's recent run of
| spectacular explosions might frustrate efforts to launch
| more nuclear-powered craft like the Voyagers too soon...
| DarmokJalad1701 wrote:
| > Meanwhile voyager is beyond the solar system
|
| Which is powered by Pu-238 - something which is in short
| supply nowadays, extremely expensive and pretty much
| inaccessible for a private company like Firefly who built
| the Blue Ghost lander.
|
| > I don't see why they didn't use something that's not
| solar
|
| Cost. NASA paid Firefly $101.5M for the Blue-Ghost 1
| contract [1]. Just the RTG used on the MSL Mars Lander cost
| $109M [2] (not counting the R&D costs).
|
| > so they aren't just littering the moon
|
| Well, right now it is harming no one. They can only be seen
| by cameras orbiting the moon. If and when humanity starts
| living on the moon, these landers will go in museums and
| will no longer be "litter".
|
| [1] https://spaceflightnow.com/2025/03/18/firefly-
| aerospaces-blu...
|
| [2] https://en.wikipedia.org/wiki/Multi-
| mission_radioisotope_the...
| perihelions wrote:
| For context, some moon rovers have radioisotope heaters,
|
| https://en.wikipedia.org/wiki/Chang%27e_4#Chang'e_lander_
| and... ( _" Both the stationary lander and Yutu-2 rover
| are equipped with a radioisotope heater unit (RHU) in
| order to heat their subsystems during the long lunar
| nights"_)
|
| https://en.wikipedia.org/wiki/Lunokhod_1#Rover_descriptio
| n ( _" During the lunar nights, the lid was closed, and a
| polonium-210 radioisotope heater unit kept the internal
| components at operating temperature"_)
|
| https://en.wikipedia.org/wiki/Radioisotope_heater_unit
| kristianp wrote:
| 14 days is a long time to keep warm something warm. That's in
| the realm of a Radioactive decay heater. That might at least
| keep things warm enough that it can wake up the next day.
| Tempest1981 wrote:
| Commercial chips have min/max temperature specs, like -20degC
| to +70degC, or perhaps -40degC to +125degC. (Not sure what
| spacecraft use.)
|
| Lunar temps can drop to -130degC to -250degC
| timhh wrote:
| It is possible to survive the lunar night. See
|
| https://space.stackexchange.com/a/67918/40677
| crazygringo wrote:
| I don't understand these photos at all. Why does it look like
| there are two suns in two of the photos -- one at the horizon and
| one above?
|
| Is one of them lens flare or something? I don't think the top one
| could be an overexposed earth because we're obviously looking at
| the earth's dark side. And in the other photo (middle in the
| galley) it looks like a little bit of the earth is eclipsing the
| second sun.
| zokier wrote:
| > I don't think the top one could be an overexposed earth
| because we're obviously looking at the earth's dark side
|
| It's Earth. Venus is also visible as small dot.
| verisimi wrote:
| No stars though.
| taberiand wrote:
| You don't usually see stars during the day
| ben_w wrote:
| Because of the atmosphere diffuses all the blue from the
| sunlight all over the place. I've seen people demonstrate
| that if you know where to point a telescope, it is just
| about possible to make out some of the brighter objects
| -- though I can't remember if that was a star or a
| planet...
|
| But in this case, the exposure is set at a level that
| even Venus isn't quite fully saturating the sensor.
| taberiand wrote:
| On the moon, the sunlight bouncing around is still enough
| to outshine the stars
| crazygringo wrote:
| Yup, it's less to do with atmosphere and more with
| exposure.
|
| Shots of stars at night have exposures of a few seconds
| to get them to appear. Shots in the daytime are more like
| 1/60 sec.
| verisimi wrote:
| Nor do you see Venus.
| crazygringo wrote:
| It can't be though. It's earth's dark side. It couldn't be
| bright like that -- it's not physically possible, right? At
| best it would be a sliver of a crescent.
|
| Also, in the other photo, there's a dark circular object
| partially obscuring. _That_ would have to be earth, no?
| Obscuring the sun, which means the object on the horizon
| is... lens flare even brighter than the sun, or something?
|
| Do people here understand my confusion? I'm not convinced the
| captions are accurate, because they seem to contradict what's
| physically possible.
| tialaramex wrote:
| > the object on the horizon is... lens flare even brighter
| than the sun, or something?
|
| This is a photo of sunset. The nature of sunset ought to be
| pretty easy to understand, from the point of view of the
| camera on a large object, the Sun seems to go behind the
| object and then it can't see the Sun any more, and we call
| this "setting". So no, the object on the horizon is the
| Sun, it's incredibly bright.
|
| I expect the problem is like with that "3.6 Roentgen, not
| great, not terrible" meme, you're assuming that a device
| (the camera) is giving you correct information but it was
| maxed out instead. The Earth looks bright from the Moon, as
| the Moon does to us. So lets call that 100% bright. Now the
| Sun is several hundred thousand times brighter. That's
| um... oh, it's 100% bright again, because we've maxed out
| the device.
| crazygringo wrote:
| > _The Earth looks bright from the Moon, as the Moon does
| to us. So lets call that 100% bright._
|
| No it doesn't, because as I've stated twice, it's the
| _dark side of the earth_ we 're seeing, because the sun
| is _behind_ it. It 's more like 1% bright, _as compared
| to the moon 's visible illuminated surface_.
|
| Think how bright the _dark part_ of a thin crescent moon
| is. That 's how bright the earth is going to be in this
| picture. Close to black, except for maybe a sliver of a
| crescent similar in brightness to the moon's surface.
|
| So again -- this photo makes no sense. Unless one of the
| two objects is just lens flare, or there's another kind
| of artifact.
| bodhi_mind wrote:
| Wide angle lens could explain it. We see the earth is not
| fully illuminated in one of the pictures. And the "curve"
| of the lunar surface is most likely from wide angle lens.
| crazygringo wrote:
| No, wide angle lens has nothing at all to do with
| exposure or illumination. That wouldn't explain anything.
| bodhi_mind wrote:
| You're stuck on being certain we're looking at the dark
| side. My point of wide angle lens is maybe we're _not_
| looking at it in a crescent state after all, the angles
| just appear that way due to the lens. You can see the
| illumination state in the other photos.
|
| I'm not sure what you're proposing, that this is a fake
| image?
| crazygringo wrote:
| I'm not "stuck" on it being the dark side. Of course I'm
| certain it is, that's how the solar system works. It's
| how _shade_ works. The sun isn 't _in between_ the earth
| and the moon, or else we wouldn 't be here commenting on
| HN. ;)
|
| I'm pretty sure I solved it, see:
| https://news.ycombinator.com/item?id=43452888
|
| Not a fake image, but a totally incorrect caption.
| vachina wrote:
| I know you're feeling crazy right now, im too appalled at
| HNers inability to comprehend such simple logic and yet
| sound so confidently wrong at the same time.
|
| How is it possible you're looking at a light source, and
| still see the shadow of an object shining? Right? Unless
| there is another very bright light source behind, which in
| this case there isn't.
| crazygringo wrote:
| Thank you for the validation! I was starting to think I
| was taking crazy pills.
|
| I believe I have solved it, I described it in another
| comment:
|
| https://news.ycombinator.com/item?id=43452888
|
| tl;dr: The bright object _above_ is the sun, _not_ the
| earth. The bright "object" on the horizon is a
| "doubling" reflection of the sun in one of the camera's
| lenses. It doesn't exist in reality. This happens when
| photographing the sun on earth as well with certain
| lenses. The earth is black and totally invisible, except
| that it's a tiny partial eclipse covering up a tiny bit
| of the sun at the top (clearer in other photos), which is
| why it's a little "flat" at the top. The photo is _not_
| the precise moment of sunset. The caption is entirely
| wrong.
| JumpCrisscross wrote:
| Sun on the horizon, Earth above it. (See caption.)
| croisillon wrote:
| Eu so queria te contar
|
| Que eu fui la fora e vi dois sois num dia
|
| E a vida que ardia sem explicacao
| gus_massa wrote:
| [This is part of the lyric of a song
| https://www.musixmatch.com/es/letras/C%C3%A1ssia-
| Eller/O-Seg... This kind of comments are usually downvoted
| here.]
| lolc wrote:
| They say there are sun, earth and Venus in the shot. So the
| second most bright thing must be the earth.
|
| I assume the earth here is simply blown out from overexposure.
| With my digital camera I can overexpose a new moon if I set the
| exposure long enough. So I guess it works the other way too.
|
| Edit: Actually it looks like the moon surface is already mostly
| in the shade with the hills illuminated from the back. There
| must be a hill behind the lander. So this light was reflected
| twice and is rather weak. On the left there are some higher
| hills still in direct sunlight, they are blown out. Meanwhile,
| light from earth is reflected twice, but at an acute angle.
| crazygringo wrote:
| > _I assume the earth here is simply blown out from
| overexposure._
|
| That was my first thought but I don't see how that's possible
| since we're looking at the _dark_ side of the earth. It can
| 't be overexposed when it's going to be much darker than the
| surface of the illuminated parts of the moon. At most, the
| earth would have a tiny sliver of light at the edge and we'd
| see a crescent shape.
| daemonologist wrote:
| I suspect that crescent shape is so relatively bright the
| bloom/lens flare is obscuring the details of its shape and
| making it just look like a blob. There's a little bit of
| "flatness" on top which would correspond to the darker
| inside of the crescent (think of what you'd get if you did
| a threshold and dilation, except it's probably happening
| entirely in-camera).
|
| I also suspect the surface of the moon is not directly
| illuminated by sunlight, as you can see what appear to be
| brighter (higher elevation? more "westerly?") areas of the
| surface in the distance. It might be scatter from other
| terrain or the thin atmosphere. Hard to say without more
| information - on a world with almost no atmosphere and a
| "moon" the size of earth the usual visual instincts kind of
| go out the window.
|
| There's another photo here which might be clearer:
| https://scx2.b-cdn.net/gfx/news/hires/2025/blue-ghost-
| lander...
| crazygringo wrote:
| I actually think the other photo you link does it make it
| clearer, in the opposite way.
|
| That photo shows the top bright circle clearly partially
| obscured by another dark circle of the same size. The
| only explanation is it's a partial eclipse of the sun by
| the earth. Nothing else produces that shape. And indeed,
| other photos show a full eclipse and are labeled as such,
| so we know that the timing is right! The shape is clearly
| defined -- it's not bloom or lens flare. Which means that
| _above_ the horizon we see _both_ earth and sun. And in
| the hero image, we see the same thing, as you describe it
| "a little bit of flatness". But that shape can't be
| produced by blooming a crescent. It's answered by your
| linked photo -- it's the dark, black earth obscuring the
| edge of the sun.
|
| Which leads to my original question -- _what the heck is
| the brightness touching the horizon of the moon?_ It
| simply can 't be the sun. Also, the way it dips _below_
| the horizon shows that if it is real, it actually has to
| be nearly entirely "bloom". But then the sun above
| should have way _more_ bloom and it doesn 't... which
| means it isn't a real object at all, not even a real
| reflection you'd see on the lunar surface.
|
| So I did a little bit more digging and it turns out this
| is a common effect in camera lenses, duplicating the sun.
| It's not lens flare exactly, but it's the same idea.
| Examples here on earth:
|
| https://www.reddit.com/r/Damnthatsinteresting/comments/15
| dj3...
|
| https://www.reddit.com/r/atoptics/comments/1cqk6dv/took_s
| unr...
|
| https://www.metabunk.org/threads/explained-two-suns-
| sanibel-...
|
| So this isn't sunset. The sun is above the horizon, and
| the bright "sun" touching the horizon is a reflection of
| the sun in the camera's optics. It doesn't exist in
| reality.
| lolc wrote:
| The parts of the moon in direct sunlight are blown out too.
| Where we see the terrain's texture, it's illuminated from
| the back; with what must be light reflected from the moon's
| surface.
|
| The dark side of Earth is illuminated by a full moon.
| crazygringo wrote:
| > _The dark side of Earth is illuminated by a full moon._
|
| Yes it is, but it's still going to be extremely dark.
| Think of how dark it is outside even when it's a full
| moon. You can see things, but it's still _orders_ of
| magnitude less than daylight brightness.
|
| And if the camera were exposed for minutes in order to
| not just capture that but overexpose it, we'd see stars
| _everywhere_. But we don 't. So no. Earth is going to be
| black in this picture, period, except for a possible
| crescent.
| lolc wrote:
| It doesn't take very special cameras to capture a new
| moon. I have many pictures that look like this: https://u
| pload.wikimedia.org/wikipedia/commons/thumb/1/19/Lu...
|
| For a photo like this I use an exposure of around one
| second.
| crazygringo wrote:
| I think we're agreeing -- you're using a shorter exposure
| that captures the dark part of the moon, but isn't long
| enough to capture stars.
|
| If you want to capture stars, it needs to be longer.
| Looking it up says that 20 seconds is roughly the
| minimum. Which is also around what would overexpose the
| entire moon in your example. So that's what I'm saying --
| the dark side of the earth doesn't seem like it could be
| overexposed because we can't see any stars.
| dragonwriter wrote:
| > Why does it look like there are two suns in two of the photos
| -- one at the horizon and one above?
|
| I _think_ that its a reflection (on what? internal to the
| camera optics, somehow?) In both cases, the second sun _also_
| seems to have a horizon occluding it, from the opposite
| direction.
| piker wrote:
| Is the Earth bright like that due to the moonlight reflecting
| back?
| runjake wrote:
| The photo's caption says:
|
| "This image provided by NASA/Firefly Aerospace, Tuesday, March
| 18, 2025, shows the sun setting on the moon, with Earth and
| Venus in the distance."
| magic_quotes wrote:
| Here you go: https://www.youtube.com/watch?v=IpA9DORDkeE.
|
| > we're obviously looking at the earth's dark side
|
| We are not. Why would we?
| crazygringo wrote:
| >> we're obviously looking at the earth's dark side
|
| > We are not. Why would we?
|
| Yes we are.
|
| Because the earth is in between the sun (faraway) and the
| moon (where we are) and very close to the line between the
| sun and us (because they're close by in the image -- it's not
| like the sun is in front and the earth is 90deg above us
| which would half-illuminate it, or 180deg behind us which
| would entirely illuminate it).
|
| If you turn on a lamp in a room, and hold an object between
| you and the lamp, obviously you're looking at the side of the
| object that is in shade. The illuminated side faces the lamp,
| which is _opposite_ you.
| babyent wrote:
| o7 buddy
|
| Damn I honestly feel for the lander even though it's just a
| machine lol
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