One week after opening with the best demo score for any new drama this season, ABC’s “Life on Mars” came crashing down to earth on Thursday.

The drama about a cop who is transported back to the 1970s lost about one-third of its premiere score to finish behind rival dramas on NBC and CBS. The decline by “Mars” corresponded with a solid week-two showing for the Eye’s fellow rookie “Eleventh Hour,” which capped a winning night for the net.

According to national estimates from Nielsen, “Life on Mars” settled for a 2.5 rating/7 share in adults 18-49 and 8.22 million viewers overall, a far cry from its promising premiere score (3.7/10, 11.33m). It retained just 42% of its lead-in from “Grey’s Anatomy” (5.9/15, 14.80m), which rose a bit week to week and reclaimed its standing as the night’s top show in 18-49.

In the same 10 o’clock hour, CBS rookie “Eleventh Hour” (3.2/9 in 18-49, 11.91m) ran second in 18-49 to NBC’s “ER” (3.6/10, 8.96m), matching its premiere-week delivery. But “Eleventh Hour” looked much better relative to lead-in this week, as 9 o’clock CBS drama “CSI” (5.2/13 in 18-49, 19.28m) posted a large week-to-week decline.

“Eleventh Hour” edged out “ER” for the lead in 25-54 (4.2/11 to 4.1/10) and easily topped its time period in total viewers.

Also airing for the second time Thursday was NBC half-hour “Kath & Kim” (2.5/7 in 18-49, 6.10m), which was down about 20% from its premiere. It retained 93% of its lead-in from “My Name Is Earl” (2.7/8, 6.72m), which was down a tick week to week to finish second at 8 o’clock.

Peacock’s 9 o’clock combo of “The Office” (4.3/11 in 18-49, 8.28m) and “Saturday Night Live: Weekend Update” (4.2/10, 8.83m) cooled some, placing third in most categories.

On Friday, NBC’s two-hour bow of “Crusoe” (prelim 1.6/5 in 18-49, 7.3 million viewers overall) did OK by the net’s recent low-bar standards on the night, but the Peacock was below its year-ago showing with “Deal or No Deal” and “Friday Night Lights.” One positive for “Crusoe” was that it improved in its second hour, where it will regularly be seen, beginning this week.

The night’s other rookie show, CBS drama “The Ex List” (prelim 2.0/6 in 18-49, 6.4 million), remained steady in its third week, again dropping from its “Ghost Whisperer” lead-in (prelim 2.5/9, 8.9 million) but leading its hour in 18-49. Still, it remains below what “Moonlight” had averaged in the timeslot at this point a year ago.

The 10 o’clock hour went narrowly to CBS’ “Numbers” (prelim 2.1/7 in 18-49, 8.6 million) over ABC’s “20/20” (prelim 2.0/6, 6.9 million), with NBC’s struggling sophomore “Life” running third (prelim 1.5/5, 5.9 million).