POLaR bears might have breathed a sigh of relief at Cairn Energy abandoning two more wells in Greenland, but the news was not such good news for shareholders.  Having already drilled three dry holes this year, the oil explorer yesterday confirmed that it had plugged and abandoned the final two wells drilled in 2011, further illustrating the challenges of striking black gold in the vast, little-explored terrain.  Cairn, whose Greenland programme has cost around $1bn (?637m) so far, said it would review the data gathered and that it was in discussions with potential partners about buying into its Greenland licences.  "Whilst we have yet to make a commercial discovery we remain encouraged that all of the ingredients for success are in evidence," said Simon Thomson, Cairn's chief executive.  But Richard Rose, an analyst at Oriel, said the update offered little further encouragement and he thought it "highly unlikely" that there would be any drilling in Greenland next year.  "This now concludes the latest drilling programme in Greenland which, whilst having some minor encouragement, has failed to yield a discovery," he said. He added that although the news should not be a surprise to the market, the shares were likely to come off, but this could open up a buying opportunity. after earlier sinking as low as 258.8p, Cairn later pared its losses, closing down just 2.7 at 272.3p as the large-caps staged a turnaround.  after Standard & Poor's cut its ratings on 15 major lenders, the blue-chips began the session in a grim humour. But moves by China and then the central banks prompted a recovery and the FTSE 100 finished up 168.42 points - 3.16pc - at 5,505.42 while the FTSE 250 soared 283.71 points - 2.83pc - to 10,315.29.  Sentiment was boosted by central banks taking concerted action to lower interest rates on US dollar loans, which should encourage lending between banks. as such, high street lenders reversed their earlier losses, with Royal Bank of Scotland putting on 1.47 to 20.99p. Barclays advanced 11? to 180?p.  Miners helped haul the benchmark index higher after China cut its banks' reserve ratio requirements, easing credit strains. Hopes that such a move will fuel China's demand for raw materials heartened the likes of antofagasta - up 100p to ?11.84 - and Xstrata, up 62p to ?10.17.  Insurers joined the rally, with aviva rising 8.9 to 311.7p and Old Mutual advancing 4.1 to 113.4p. Lifting the latter was a push from RBC Capital Markets, which was on bullish form following a recent visit to Old Mutual's South african business. analyst Gordon aitken said the insurer was well-placed to take advantage of "wealth and insurance penetration in the rest of africa".  Having also recently visited Prudential's asian business in Kuala Lumpur, Mr aitken thought that Old Mutual's operations had "several of the characteristics of Prudential's asian businesses, yet the valuation is markedly cheaper". Old Mutual put on 4.1 to 113.4p while Prudential rose 12? to 623p.  There was also talk that Haverford, the bidder for 25pc of Lloyd's of London insurer Omega Insurance, had replaced a proposed tender offer of between 70p and 83p-a-share with a fixed price offer of 74p-a-share. Omega shares were up 2 at 67.75p.  Only five stocks were left under water, with National Grid and Tate & Lyle trading without the rights to their most recent dividend.  Profit-taking continued to hit mid-cap Thomas Cook, with the beleaguered tour operator easing 0.61 to 18.29p following Monday's surge after the business - which has issued a string of profit warnings - secured a rescue package from its lenders.  Suffering the sharpest fall, however, was SDL. The translation software company retreated 30? to 609p as rival alterian - for which SDL recently made a 110pper-share offer - indicated that it expected double-digit revenue growth in 2013 thanks to strength in its US and asian markets.  alterian, which posted an interim loss of ?18.6m compared with ?601,000 profit last time, edged up 1? to 101?p.  Climate change consultancy aEa Technology was 0.2 - or 40pc - warmer at 0.54p. Last month, its shares tumbled after the business issued