MESSENGER News Thread, news, updates and discussion Options

[stevesliva]

... by using the helium pressurant for thrust after exhausting all its propellant. Which is neat.

[nprev]

Very innovative. I wonder if this will enable them to determine precisely when the propellant is completely exhausted, presumably by a drop in acceleration during a maneuver. Great data for reality-checking spacecraft fuel quantity models & assumptions.

[Explorer1]

They've done it again:
http://messenger.jhuapl.edu/news_room/details.php?id=271

One more will be done on March 18th (the fourth Earth anniversary of MOI)!

[MarcF]

"Two new papers from members of the MESSENGER Science Team provide global-scale maps of Mercury's surface chemistry that reveal previously unrecognized geochemical terranes -- large regions that have compositions distinct from their surroundings. The presence of these large terranes has important implications for the history of the planet."
http://www.sciencedaily.com/releases/2015/...50313110434.htm

Regards,
Marc

[Explorer1]

Press Release from LPSC: http://messenger.jhuapl.edu/news_room/details.php?id=274

And a load of media:
http://messenger.jhuapl.edu/news_room/presscon13_multi.html

[Explorer1]

The first in the final series of TCMs is complete, with some unprecedented science about to be done (like Cassini's proximal orbits).

http://messenger.jhuapl.edu/news_room/details.php?id=276

Great to see every last opportunity being squeezed out; it's going to be a long time until BepiColombo shows up.

[Doug M.]

Great to see every last opportunity being squeezed out; it's going to be a long time until BepiColombo shows up.

BepiColombo's launch date seems to have slipped by about 16 months, from August 2015 to 'early 2017', over the last few years. They're still claiming a January 2024 arrival date on the ESA home page, but I'm not sure if that's realistic. "Ten years, give or take, if all goes well" seems like a reasonable estimate right now. So, yes, let's delight in this last surge of data! The investigation into Mercury's paleomagnetism is particularly interesting.

-- Meanwhile, a question. At these low periapses, MESSENGER is zooming along pretty fast. I recall there was some discussion that blurring could be an issue. Is it still, or was that resolved?


Doug M.

[Explorer1]

The press releases look as sharp as ever, so I would assume so.

[tedstryk]

I wonder how low it will go before impact. I have dreams of it nearly skimming the surface (even if images are smeared) on a final orbit before the end. Unlikely, but cool if it happened.

[djellison]

Based on the trajectory data we've been given for Eyes on the Solar System.... single digit km's in altitude - 5km or so.

[Doug M.]

Press Release from LPSC: http://messenger.jhuapl.edu/news_room/details.php?id=274

Coming a bit late, but this caught my eye:

"MESSENGER's low-altitude campaign has enabled imaging of the polar deposits in the permanently shadowed floors of Mercury's near-polar craters at higher resolutions than ever previously obtained, says Nancy Chabot, the Instrument Scientist for MESSENGER's Mercury Dual Imaging System (MDIS) and a planetary scientist with APL.

"Acquired with the broadband filter of MDIS, low-altitude images show that the deposits have sharp, well-defined boundaries and are not disrupted by small, young impact craters," says Chabot. "These characteristics indicate that the deposits are geologically young. This inference points either to delivery of volatiles to Mercury in the geologically recent past or to an ongoing process that restores the deposits and maintains the sharp boundaries."

So, not only does Mercury have polar ice deposits, but they seem to be geologically young? (Do we know how that compares to the Moon? We don't, right?) And that throwaway "ongoing process" comment...


Doug M.

[Phil Stooke]

This specific observation, of ice patches (in fact seen not just in this crater but in several others) with distinct albedo boundaries and sharp edges, has not been repeated on the Moon, where imaging doesn't seem to show the same type of surface deposit. It's assumed that on the moon the volatiles are more mixed into the surface. In either case, though, the detected volatiles must be young, probably actively replaced, to counteract the effects of micrometeorite erosion. The ongoing process might be cometary impacts (episodic but ongoing), or solar wind implantation in the regolith followed by redistribution, or loss of interior volatiles, maybe associated with those weird hollows.

Phil

[Paolo]

I wonder how low it will go before impact.

this graph should at least give an idea

[Explorer1]

Meanwhile, 4,000 orbits completed...

[Doug M.]

This specific observation, of ice patches (in fact seen not just in this crater but in several others) with distinct albedo boundaries and sharp edges, has not been repeated on the Moon, where imaging doesn't seem to show the same type of surface deposit. It's assumed that on the moon the volatiles are more mixed into the surface. In either case, though, the detected volatiles must be young, probably actively replaced, to counteract the effects of micrometeorite erosion. The ongoing process might be cometary impacts (episodic but ongoing), or solar wind implantation in the regolith followed by redistribution, or loss of interior volatiles, maybe associated with those weird hollows.

Hadn't thought of solar wind implantation, which of course would be an order of magnitude stronger on Mercury. Loss of interior volatiles would be interesting too -- there's evidence for at least occasional small-scale recent-ish volcanic activity on Mercury. And we know Mercury had pyroclastic eruptions, which hint at significant levels of volatiles in the mantle. (IIUC, that's been a head-scratcher, because the favored models for Mercury's formation and evolution predicted volatile depletion.)

Also, if I'm reading the paper abstracts right, it looks like there's a second line of support for the ice being geologically young: apparently there are craters that should be too small and/or too far south to hold ice over gigayear time scales, but that nonetheless do seem to hold ice.


Doug M.