Australia 4 for 165 (Smith 64*, Marsh 44*) trail England 302 (Vince 83, Malan 56, Stoneman 53) by 137 runs
Scorecard and ball-by-ball details
An absorbing Ashes contest will go into the third day with neither side having made a convincing grab for the upper hand, but with Australia's captain, Steven Smith, firmly ensconced as the most vital performer of the contest to date. His hard-bitten half-century, with determined support from the recalled Shaun Marsh, hauled Australia towards a position of parity, having clawed back the initiative in the latter half of England's own innings only for their own top-order to crumble in a gripping passage of mid-afternoon action.
Having inched along to 4 for 196 on a cat-and-mouse opening day, England made it through the first hour of an elongated morning session without further loss, as Moeen Ali and Dawid Malan carried their fifth-wicket stand to 83. But thereafter, wickets tumbled like the Barmy Army's sobriety levels - 6 for 56 as England's innings shuddered to an underwhelming 302 all out, before Australia put that total in some sort of context by slumping themselves to 4 for 76 in reply.
But, having lost the fourth of those wickets - Peter Handscomb - in the first over after tea, Smith and Marsh found the depths of resolve that their team required, first to guard against disaster and then, in compiling an unbroken 89-run stand spanning 37 overs, to leave to England sweating for further breakthroughs as the shadows began to length.
Marsh, back in Australia's Test team for the eighth separate occasion, grew in confidence as his stay was extended, but was restricted to two scoring shots from his first 36 deliveries as England hounded his defences, with Moeen called back into the attack to challenge his weakness against the turning ball, and James Anderson serving up a typically inventive spell of swing and seam in which no two deliveries seemed entirely alike, except that they were invariably targeting the top of off stump.
But it was Smith, inevitably, who applied the stamp of class to Australia's innings, and in so doing, he carried his career average in home Tests up into the 70s. He too was obliged to dig deep for long periods - having chiselled his first boundary from his third delivery, he didn't add his second until 24 overs later. A top-edged hook off Chris Woakes was the closest he came to giving his stay away (the ball plugged safely in no-man's land at deep midwicket), but he added a second boundary off his hips one ball later, and having brought up his fifty from 112 deliveries, reached the close looking as solid and ominous as any batsman can be.
Of the 41 times that Smith has previously reached a half-century, he has converted to three figures on a remarkable 20 occasions - and that, in the final analysis of what is already a keenly fought contest, could be the making of a decisive difference between the teams. For while England's own performance had been chock-full of promise on three distinct occasions, the abiding tale of their day's batting was the hasty manner in which it came to an end, with the last six wickets tumbling - their fourth bona fide batting collapse in as many innings on tour.
Not that Australia found the going any easier when their turn came to bat. The pitch seemed markedly quicker than it had been on the opening day, and England's first breakthrough was delivered, as so often in recent Ashes contests, by Stuart Broad, who found some extra zip outside the off stump of the debutant Cameron Bancroft, for Jonny Bairstow to swallow the thin nick and send him on his way for 5.
Anderson also threatened the edge with a disciplined new-ball spell, but the arrival of Usman Khawaja at No. 3 prompted Joe Root to take an early look at the offspin of Moeen - emboldened, no doubt, by the earlier success of Nathan Lyon, who had been the pick of Australia's bowlers in spite of his underwhelming figures of 2 for 78.
Khawaja's career has been scattered with failures against fingerspin - he lost his Test place in the subcontinent due to doubts about his technique - and sure enough, Moeen needed just two deliveries to bag his man. Khawaja watched one turn appreciably past his off stump, then had no answer whatsoever to a tighter, fuller follow-up that pinned him lbw for 11.
Warner, by this stage, was settling into his groove - without ever letting rip with his full power and fury, he had nevertheless greeted Moeen with a rasping drive for four, and had eased along to 26 when the unassuming seam of Jake Ball did him like a kipper. Latching onto a back-of-a-length delivery, Warner swivelled into a half-hearted pull, and Malan at short midwicket juggled briefly before clinging on at the second attempt.
And then, five balls after tea, Anderson claimed a deserved first scalp of the series as he out-thought the crease-bound Handscomb with a brilliant variation ball - part yorker, part fast offbreak, that burst off the turf and into his shin to prompt a vociferous appeal and a successful review, after umpire Aleem Dar had initially judged it to be sliding down the leg side. But the stage was set for Smith and Marsh to embark on their vital revival.
It was a vital riposte from England, whose own batsmen looked at one stage to have had laid the foundations for a formidable total. But, despite having kept Australia in the field for 117 overs, their tactic of prioritising time over intent was undermined by a series of injudicious dismissals, as they tumbled from 4 for 246 to 302 all out in a harum-scarum display.
The momentum swing was initiated at precisely the moment when it seemed that Australia were running short of ideas. Despite resuming with a new ball that had been a mere three deliveries old, Australia's seamers found themselves thwarted by Moeen and Malan, and when Starc returned for his second spell shortly after the drinks break, he opted for a barrage of short balls that appeared to be an optimistic approach given the sluggish nature of the deck.
It did not appear to have fazed Malan in the least, the third of England's Ashes debutants to make his mark with a half-century. But, undeterred, Starc persisted with his approach, found some extra height to take the delivery out of Malan's comfort zone, and Marsh at square leg - whose previous involvement had been to rip Starc's trousers with his studs in an awkward tangle in the outfield - clung onto a top-edged pull to deliver Starc his 150th Test wicket.
Eight deliveries later, England were left with two new batsmen on 0 when Moeen stretched forward to the persevering Lyon, and was pinned lbw for 38. Four balls later, Lyon had a second, as Woakes gave himself room to drive against the spin and inside-edged another big turner into his stumps for a duck. England had shed three wickets for four runs in the space of 18 deliveries, and much as had been the case when a Peter Siddle hat-trick wrecked their first innings at the Gabba in 2010-11, their innings had been reduced to pure damage limitation.
Bairstow was, on this occasion, unable to stem the flow, top-edging a steepler to Tim Paine behind the stumps for 9. Ball gave it some humpty to enliven England's muted fans, tonking a couple of boundaries before trying to flick Starc off his pads, only to be brilliantly caught by a flying Warner at leg gully for 14.
That wicket fell in the scheduled final over before lunch, meaning that play was extended by half an hour as Anderson came out to join Broad. Anderson, not unusually, was the subject of a barrage of verbals and bouncers, one of which he heaved deftly over the cordon for four. Broad, meanwhile, should have been dismissed at fine leg to signal the end of the innings, only for Marsh to spill a dolly over the boundary for four. However, his luck could not last, and where Marsh had erred, Handscomb displayed safe hands to give Josh Hazlewood his first wicket of the series.