Hi Morgana:
I asked myself the same question. But in "Strange Vistor" where Trask comes to the Daily Planet and gives lie detector tests, when Clark gets in the warehouse on Besollo Blvd and finds his ship he finds the ball with the image of Earth turning to Krypton. The dialog is here:
CLARK
Gingerly runs his fingertips down one metal beam. On it are
a row of mysterious hieroglyphics. At the end of the row:
the familiar "S" insignia he has begun to wear on his
Superman costume. It's a moment of epiphany causing even
Clark's superpowered knees to buckle.
Next to the wreckage is a bagged artifact, labelled,
"Smallville, Exhibit A." Inside is what appears to be a
small ball. Clark takes it out of its bag, and as his
fingers make contact, it begins to &low from the inside.
It is a three-dimensional globe with mountain peaks and
valleys. It's Earth. Clark's face shows the effect the
moment is having on him. When we see the globe again, it
is different. Peaks and valleys, reddish tint, huge ice
caps. It is another planet. Clark, stunned, says to him-
self in a soft whisper of recognition of a world long for-
gotten and a memory long suppressed:
CLARK
Krypton.
All of this is our version of Rosebud, and Clark is nearly
overwhelmed by emotion. Snapped out of it by:
LOIS
Clark!
Clark quickly pulls the tarp back over the spacecraft.
Lois can't see this. Clark stuffs the ball in his
pocket.
So in the first episode after the pilot Clark knew about Krypton.
Artemis
