Will LAGEOS burn up or be destroyed on impact?

Question

The LAGEOS satellites have plaques that try to explain what they are without using any words or decimal numbers or similar 'current' concepts.

To me, this suggests we expect the satellites to last their full lifetime, as the technology to find them in space will surely exist in much shorter time-scales (a few thousand if not hundreds of years, when we might expect English to still be understood in some way).

But when they de-orbit I'd expect them to either burn up or be destroyed when when they impacted the earth's surface.

So: am I wrong assuming that we think they'll last their full lifetime, or am I wrong assuming that they'll be destroyed on impact?

Edit: the lifetime of these satellites is expected to be around 8m years, but for the purposes of this question lets assume that structure of the earth, atmosphere and solar system is pretty similar to now.

This answer says that the orbital lifetime of LAGEOS is projected to be 8 million years. Are you asking what will happen after 8 million years? — called2voyage, May 19 '16 at 15:42
@called2voyage yes - is that so crazy? See edit, let's ignore questions about whether the earth actually exists in its current form. — stripybadger, May 19 '16 at 15:53
That's fine, I just wanted to be sure you were aware of that. — called2voyage, May 19 '16 at 15:53
@called2voyage I read the question as, when the LAGEOS satellites finally do deorbit, do we expect them to survive reentry and landing sufficiently intact that the markings on the plaques will remain discernable to a possible future civilization coming across the remains of the satellites. — user, May 19 '16 at 15:53
@MichaelKjörling I understand that, I'm just concerned that even though the plaques are stainless steel, they may not be readable in 8 million years even if the probe remains intact on impact. — called2voyage, May 19 '16 at 15:59
@called2voyage Certainly fair enough. Orbital stability and satellite longevity are two vastly different matters to begin with. — user, May 19 '16 at 16:01
Good points about longevity - if the survival of the plaques is in question then it probably invalidates the premise of my question anyway. — stripybadger, May 19 '16 at 16:32
I assumed that Dr. Sagan had in mind that the satellites would be retrieved from orbit at some far-future time. — Organic Marble, May 19 '16 at 16:39
@OrganicMarble That's what I was thinking as well: orbital retrieval, as opposed to crash site retrieval. — called2voyage, May 19 '16 at 16:52
These are rather hefty - with r = 30cm and m = 400,000g the average density is ~3.5 g/cm^3. Estimating from this video they are a large solid brass cylindrical core inside a solid Aluminum sphere with roughly half the mass from each. Since Al melts around 660C and Brass around 1000C, I wonder what happens to a ball of liquid metal on re-entry - sounds spectacular! — uhoh, May 29 '16 at 01:24

score 1 · Answer 1 · answered May 19 '16 at 17:42

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The satellite is made from aluminum and brass, so I expect it will be burned up in the atmosphere when it reenters. The only chance it has of being read is if someone goes and picks it up, or at least gets a really big telescope.

answered May 19 '16 at 17:42

PearsonArtPhoto

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The plaque is inside the probe. I'm interested in what kind of telescope you're using to read it. – called2voyage May 19 '16 at 17:44
Well, micrometeors might destroy part of it, but leave the plaque intact? – PearsonArtPhoto May 19 '16 at 18:00