Such is the enthusiasm for Formula 1 in Brazil that commentating legend Murray Walker once suggested the country’s mothers breast-fed their offspring on the finest hi-octane. Seldom has the F1 paddock heard truer words spoken in jest, for not only did Brazil deliver triple champions Nelson Piquet, Ayrton Senna and 1972/4 champion Emerson Fittipaldi - plus various GP winners - but Sao Paulo also simply oozes F1 passion.Despite Brazil not being a wealthy country and the Interlagos circuit having among the highest ticket prices of all due to the eye-watering costs of shipping cars and kits at least 11 flight hours south whether from last week’s GP in Austin or directly from Europe, the circuit – named after the lakes within which the oval circuit nestles – is invariably packed with cheering, flag-waving crowds.EXTREMELY BUMPYIn short, after the longest and most gruelling season in F1 history, the ferociously fast circuit in one of Sao Paulo’s seedier suburbs provides the ideal venue for a championship showdown – as thrilling season finales here in 2006, 2007 and 2008 proved. The last time a title went down the wire was 2010 in Abu Dhabi, and what a dreary affair that turned out to be despite the two main protagonists being then, as in 2012, Red Bull’s Sebastian Vettel and Ferrari's Fernando Alonso.The extremely bumpy 4.309km Interlagos circuit is one of the shortest on the trail but also one of the most technically challenging. It is characterised by its anti-clockwise direction, constantly high g-force, fast corners, hairpin bends, dramatic elevation changes and a foot-flat blast along the arcing final section.Interlagos was carved into a hill to provide a natural amphitheatre with superb views over the entire circuit. It has 15 turns (10 left, five right), two of which are taken at less than 100km/h, two at more than 250km/h. The pits lane runs to 360m and takes 13 seconds to cover at the 100km/h permitted during a race (60 during preliminaries) to which must be added standing time of 2.5sec to estimate pit-stop penalties.TEMPERATURE CHALLENGEThe fastest section of the circuit is the 16sec full-throttle blast along the arc from Turns 14/15 to Turn 1, which drops away abruptly as the cars shed more than 200km/h within seconds to negotiate the off-camber 90° left-hander. Cars will be at full throttle for 70% of each lap – more than at any other circuit – although speeds are balanced by six braking events, three of them "heavy".Pirelli had specified its Medium (white sidewalls) and Hard (silver) compounds, as in Texas, but with forecast temperatures in the mid-twenties getting tyres to their operating window should not prove anywhere near as challenging as in Texas, where an unseasonal 20 prevailed.However, Pirelli’s dry compounds may not see much use if the weather, always unpredictable in this tropical, high (800m above sea level) region, turns out as forecast: 25 degrees and ferocious thunderstorms on Saturday afternoon, light rain on Sunday afternoon. That said, despite Sao Paulo’s reputation for unsettled weather, rain fell on only three of the previous 10 races.Although the FIA had not specified the DRS zone by the time of writing, it is likely to be a single zone (as in 2011) with mid-Turn 2 detection and activation 70m after Turn 3. Thus the zone will be around 600m long, making overtaking possible - but not easy. YOUNGEST TRIPLE CHAMPHistorically, six of the previous 10 Brazilian GP's have had pace-car interventions; eight were won from the front row but only two from pole. The 2003 winner came through from eighth on the grid in a race blighted by torrential rain…All eyes will be on Vettel and Alonso, one of whom will on Sunday make history by becoming the youngest triple champion in F1 history, although the former also stands to become the only living driver besides Michael Schumacher who will retire (again) after this race after a disappointing three-season comeback with Mercedes, to make it three in a row.With Vettel holding a 13-point advantage over his nemesis there are various permutations (see below) but the simplest way of calculating Alonso’s odds of lifting the title are that he must win with Vettel out of the top four.A tall order, that, and one the Spaniard is unlikely to deliver on current Ferrari performances. For three years now Ferrari hasn't been able to provide arguably the best driver of his generation with a title-winning car; heads will surely roll if Ferrari fails again…Red Bull has the very real prospect of alternator issues; not only did failure of the Renault-supplied device twice stop Vettel in his winning tracks earlier in 2012 but it failed on team mate Mark Webber’s car last weekend in Austin, costing the lanky Australian a podium shot. Alternators have caused other Renault-powered cars this season so it is extremely worrying for Red Bull and potentially devastating for the French automaker.OUTSIDE INTERVENTIONEqually worrying for each contender is the very real prospect of other front-runners (totally legitimately) intervening in the title battle. Austin's winner Lewis Hamilton did so in Austin and Kimi Raikkonen (Lotus) in Abu Dhabi. They clearly have nothing to lose and everything to gain… Sunday’s 71-lap race and Saturday qualifying are scheduled to start at 6pm SA time – weather permitting. Thereafter F1 will shut down until the first tests/launches scheduled for February 5, 2013, in Jerez, Spain.Here's how the Vettel/Alonso duel stands:VETTEL WINS THE TITLE IF:- He finishes in the top four.- He finishes fifth, sixth or seventh and Alonso doesn't win.- He finishes eighth or ninth and Alonso is third or lower.- He finishes 10th or worse and Alonso isn't on the podium.ALONSO WINS THE TITLE IF:- He wins and Vettel is fifth or lower.- He is second and Vettel eighth or lower.- He is third and Vettel is 10th or worse.