This is an exceedingly long shot, but since there are no other answers it might be worth a try. I wonder if this is a misremembering of a short story by John Wyndham called The Red Stuff.
The problem is that the "stuff" is red, not silver like mercury, and the action takes place on an asteroid called Pomona Negra not Mercury. Apart from these (rather large!) disagreements the story is pretty similar.
In The Red Stuff a message globe (a form of emergency beacon) is found in the asteroid belt. It comes from a ship called Joan III and describes the ship's encounter with a mysterious red substance and how the ship was forced down on the asteroid Pomona Negra.
The ships Annabell and Circe are sent to rescue the Joan III, so this matches your description of the search for a missing ship. When they get to Pomona Negra they find it completely covered by the red goo. The Circe attempts to take a sample but the goo sends out a blob to trap the ship:
A sort of tide or tremor in roughly circular ripples seemed to be running through the mass. At first Bentley attributed it to the impact of the sample bottles which, he judged would now have been propelled into the substance, and thought it in consequence to be in a much more liquid state than he had hitherto imagined. Then he realized uneasily that the ripples were not spreading outwards as from a stone dropped into water, but inwards.
...
The stuff had gathered in a kind of mound beneath the Circe , and flung out towards her a vast shapeless limb of itself, a reaching pseudopod like a licking red tongue.
The Circe does try to ascend as fast as possible, but doesn't make it:
Those on board wasted no time. There was a gush from the Circe's main tubes, and she leapt forward like a flash. But swift as she was, she did not draw clear in time. She tore through the top of the extending tongue like a streak and emerged from it with speed undiminished, but she was no longer a silver ship: from bow to tubes she was coated in brilliant scarlet.
The two ships manage to clear the red goo off the Circe by having the Annabell play its thrusters over the Circe and burn the surface of the ship clean. The two ships give up hope that anyone from the Joan is alive below the sea of goo and return to the Lunar base. But ...
The sample of goo taken by the Circe leaks while in storage on the Lunar base and the story ends with the desperate fight to stop the Moon being consumed by the red goo just as Pomona Negra was.
The story was written in 1951 so 30 years ago it would already have been an old story, but you could have read a reprint. As I said, this is a long shot and probably just a coincidental similarity in the plots. But it's just possible you might have misremembered the story or conflated it with some similar story.
For what it's worth, I remember being terrified by the story when I read it as an eleven year old, and having just reread it I'd say it stands up pretty well even now 65 years later.
