Mercury's shadowy North Pole revealed by M-CAM 1 | Hacker News Reader

Mercury's shadowy North Pole revealed by M-CAM 1

esa.int

81 pointsdivbzero15 comments

The ESA's article claims to "reveal" Mercury's shadowy north pole, yet the image provides no actual insight into the pole itself, which remains shrouded in permanent darkness... The term "revealed" feels more like marketing spin than substance, as the image merely captures the general area around the pole.

This framing is reminiscent of similar oversights in planetary science, such as the perplexing case of Mars' north pole. Studies suggest a cyclical process where subsurface vapor escapes through a thinned crust during colder seasons, freezing into massive ice deposits, like those seen in the Korolev Crater. These ice layers, some over 1.2 miles thick (see the ESA Korolev Crater Study), challenge the traditional narrative of Mars' geophysical activity. Observations from missions like Mars Express and Mars Reconnaissance Orbiter reveal hints of dynamic interactions between the crust and atmosphere, yet much of this is glossed over in mainstream discussions.

Why is there a persistent pattern of incomplete or opaque presentations regarding planetary poles? The public deserves transparency and detailed interpretations, not handwaving claims. If the evidence of crustal thinning and volatile release is as compelling as the imagery suggests, why the reluctance to address it head-on???

A commitment to clarity would foster trust in scientific institutions, rather than leaving informed observers to speculate about what's being left unsaid. This is frustrating.

IMHO using “north pole” in a headline to mean “north polar region” tells us more about the nature of headlines than about the quality of science reporting.

With labels describing the surface features: https://www.esa.int/ESA_Multimedia/Images/2025/01/Mercury_s_...

Absolutely love the ESA Like button in the article. Conveys the feeling it's designed by a flight instruments engineer rather than a social media frontend person (make sure to click it twice).

You tricked me

If you refresh the browser the button is unpressed, but when you press it again it gives a stern message about liking twice.

>M-CAM 1 took this long-exposure photograph of Mercury's north pole

I'm curious how this works. The dynamic range between the sunlit parts and the dark portions must be huge at that distance from the Sun. Anyone have the technical details on the camera or post processing they use to achieve this? Is it really a long exposure or is it a series of photos at different exposures stitched together?

Edit: details at the bottom seem to imply a single photo, but that "long exposure" really isn't that long

>This image of Mercury's surface was taken by M-CAM 1 [...] using an integration time of 40 milliseconds.

Integration implies multiple pictures taken and stacked. This is how we do deep sky astrophotography on our back yards.

I think this is their terminology for exposure time. The sensor is integrating charge from incident photons during this period. Of course the image could be stacked also!

Edit: the sensor is integrating CURRENT. Charge is the integral!

Integration over time and integration over bit fields are both ways we do deep sky astrophotography. Integration over time is used to collect more photons without saturating sensor wells and integrating bit fields (stacking) is used to increase signal to noise

What does that mean exactly? What's the relation between integration time and exposure time?

Wondering same. If my math is right, this was a 1/25 sec. exposure. (40/1000)

If you're thinking that long exposure automatically means something longer than 1 second, it might not mean long exposure to you.

I'd guess this is a fixed aperture system where the main way to control the exposure is with shutter speed. But for images taken in bright sunlight, you can use shutter speeds 1/250, 1/1000, 1/2000, or even higher type numbers. In those terms, 40 milliseconds is 10 times slower/longer than 1/250.

So for the M-CAM 1 system, 40 milliseconds could be an extremely long exposure

I was curious as to whether its north pole is always inclined away from the sun, as it could be if mercury is in synchronous rotation around the sun. It turns out that it is not: it has a 3:2 spin–orbit resonance, rotating three times for every two orbits. On the other hand, its axial tilt is small - only 0.034 degrees [1], which I suppose means that the pole is always close to the terminator - but, as the angular size of the sun as seen from mercury is always a bit over a degree [2], I think that means some fraction of the sun's disk would always be above the horizon at the north pole (unless it is in a crater.)

Update: From this map [3], the pole appears to be on the rim of the crater touching crater Tolkein on the latter's right (see ahazred8ta's comment for a link to an annotated copy of the photograph), and in the photograph, that part of the rim is illuminated.

[1] https://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact....

[2] Data from [1] and https://en.wikipedia.org/wiki/Sun:

   Solar radius: 7e8 M
   Mercury aphelion: 7e10 M
   Angular radius at aphelion = arctan 0.01 = 0.57 degrees.

[3] https://pubs.usgs.gov/sim/3404/sim3404_sheet2_.pdf

I would have expected a larger crater for Tolkien..

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