I'm sorry if thread necromancy is considered a black art around here, but this is a subject I've been interested in several times, and I have some thoughts to share.
Footprints in sand are the very epitome of impermanence. Generally speaking, they dry out and blow away, or are obscured by the tide within twelve hours. But there is a trackway at Laetoli of proto-human footprints 3.6 million years old, half a dozen sites around the world there are fossilised dinosaur trackways up to about 100 million years old. Which just goes to show that nearly anything can be preserved for geologically long times in favourable conditions. Eggshells, insect wings, the ossicles in the middle ears of early mammals the size of mice: these have all been preserved in some instances for 100 million years or more.
The most important thing for preserving delicate objects through geological time is to get them buried quickly in a neutral or slightly basic sediment. UV light, wind-born abrasive grains, freeze-thaw cycles, glacial abrasion, fire, and acidic surface water are the major causes of damage to paleaontological wannabes. And anything buried in an area of tectonic uplift will be brought to the hostile surface in time. But in an area of gradual subsidence, with continual accumulation of sediment, incredibly delicate things can survive.
If ossicles and eggshells can survive a hundred million years, how long are ceramics going to last? Bricks and the glass or ceramic insulators from high-voltage power lines are chemically inert and mechanically robust. Facets on corundum and diamond gemstones are going to last for a long time. Gold and platinum jewelry and ingots will survive until mechanically damaged even in acidic conditions. Stainless steels will last a long time in basic conditions, as will titanium and some other metals. Concrete (the foundations of dams, for instance) will survive indefinitely in limy soil. Some roadway and railway cuttings and embankments will last for tens of millions of years if they are buried in sediment.
Space is a rather hostile environment. Sandblasting by micrometeroids will chew through anything in time, and few constructions are likely to last a million years. And the radiation will eventually chemically alter most materials, and blur the dopants in microelectronics. But buried under a few metres of the regolith of a moon or asteroid, or under a few tens of metres of ice on an ice moon the only major danger is from asteroid collisions.
Lives of great men all remind us,
We can make our lives sublime,
And, departing, leave behind us,
Footprints in the sands of time.
We can make our lives sublime,
And, departing, leave behind us,
Footprints in the sands of time.
Footprints in sand are the very epitome of impermanence. Generally speaking, they dry out and blow away, or are obscured by the tide within twelve hours. But there is a trackway at Laetoli of proto-human footprints 3.6 million years old, half a dozen sites around the world there are fossilised dinosaur trackways up to about 100 million years old. Which just goes to show that nearly anything can be preserved for geologically long times in favourable conditions. Eggshells, insect wings, the ossicles in the middle ears of early mammals the size of mice: these have all been preserved in some instances for 100 million years or more.
The most important thing for preserving delicate objects through geological time is to get them buried quickly in a neutral or slightly basic sediment. UV light, wind-born abrasive grains, freeze-thaw cycles, glacial abrasion, fire, and acidic surface water are the major causes of damage to paleaontological wannabes. And anything buried in an area of tectonic uplift will be brought to the hostile surface in time. But in an area of gradual subsidence, with continual accumulation of sediment, incredibly delicate things can survive.
If ossicles and eggshells can survive a hundred million years, how long are ceramics going to last? Bricks and the glass or ceramic insulators from high-voltage power lines are chemically inert and mechanically robust. Facets on corundum and diamond gemstones are going to last for a long time. Gold and platinum jewelry and ingots will survive until mechanically damaged even in acidic conditions. Stainless steels will last a long time in basic conditions, as will titanium and some other metals. Concrete (the foundations of dams, for instance) will survive indefinitely in limy soil. Some roadway and railway cuttings and embankments will last for tens of millions of years if they are buried in sediment.
Space is a rather hostile environment. Sandblasting by micrometeroids will chew through anything in time, and few constructions are likely to last a million years. And the radiation will eventually chemically alter most materials, and blur the dopants in microelectronics. But buried under a few metres of the regolith of a moon or asteroid, or under a few tens of metres of ice on an ice moon the only major danger is from asteroid collisions.
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