It found 100 times more water in the beads than has been measured before...

[Volcano1985]

It found 100 times more water in the beads than has been measured before, and suggests that the Moon once held a Caribbean Sea-sized volume of water.

Shouldn't it have been:

It found 100 times more water in the beads than had been measured before, and suggests that the Moon once held a Caribbean Sea-sized volume of water.

[Raymott]

It found 100 times more water in the beads than has been measured before, and suggests that the Moon once held a Caribbean Sea-sized volume of water.

Shouldn't it have been:

It found 100 times more water in the beads than had been measured before, and suggests that the Moon once held a Caribbean Sea-sized volume of water.

No, the original is correct. Without "before", you'd have to write "had".
If someone said, "It found 100 times more water in the beads than has ever been measured", you could (pedantically)object that that amount has been measured, or the statement couldn't be made. With the addition of "before", there's no logical contradiction.

A: "Has this amount ever been measured."
B: "Yes, we just did that. Do you mean before?"

A: "Has this amount ever been measured before?"
B: No.

A: "Had this amount ever been measured before?"
B: "Before what? Do you mean before this time? No, that's what we're saying. This amount has never been measured before."