Who were the stars of wet practice?

There are occasionally moments in Formula 1 that make you stop and look twice. Did that really happen? They are fleeting. Snapshots in time. But they stay with you.

I enjoyed one during the first free practice session for the 2016 Australian Grand Prix, which was almost worthless for reading the weekend's emerging form but proved priceless for watching F1 drivers at their best.

During the last 15 minutes, when most cars were on track attempting to get some precious dry running in, everyone was caught out by another of Friday's impromptu Melbourne downpours.

"Wet, dry, slick, greasy, bit drier, more wet. It changed a lot," says Daniel Ricciardo, who knows all about the idiosyncrasies of Australian weather. "Today was the definition of Melbourne - four seasons in one day is what everyone says, and we got that."

The weather was indeed tricky to read, and the wind fierce, but this created the kind of conditions that can make F1 drivers look like instant heroes or total zeroes: slick-tyre running on a changeable track surface.

The calendar shift that has brought the start of the season forward by two weeks means many teams are marginal on spare parts, and most drivers sensibly backed off to return to the pits at the first signs of this late-session rain.

But some - notably Felipe Nasr, Jenson Button and the Red Bulls of Ricciardo and Daniil Kvyat - stayed out and kept on trying.

This commitment was impressive in itself, as the track was extremely treacherous, amplifying the difficulty of the approach to my vantage point at Turn 6, which snakes slightly between the trees and is not a place where spotting your braking point and apex is simple.

"It's really difficult," says Renault's Kevin Magnussen. "Today has been very special in terms of it raining in some parts of the track. It's not Spa, it's not that big, but still you had half the track wet and the other half dry.

"Also there are all these white lines and they get really slippery, and it's bumpy, and there are a lot of shadows because of the trees.

"There will be dry and wet patches for a long time even when it's fast on slicks. That makes it a bit tricky in these conditions.

"When it rains it becomes a proper street circuit, like Monaco."

The changeable conditions combined with the difficulty of the circuit in this weather immediately caught out Williams's Valtteri Bottas and Manor rookie Rio Haryanto, who both skated off into the gravel at Turn 6 but were fortunate enough to return to the pits.

I also saw Max Verstappen loop his Toro Rosso under acceleration, and of course Nico Rosberg later crunched his Mercedes against the wall a bit further round in the wet conditions of second practice.

Button has displayed his mastery of slicks-in-the-wet conditions many times before. Recall his sublime last-lap victory in the sensational 2011 Canadian GP, or his narrow triumph over then McLaren team-mate Lewis Hamilton in the Chinese GP of 2010.

He was his usual impressive self here in Australia, less than a tenth slower than McLaren-Honda team-mate Fernando Alonso.

But there was another driver who stood out head and shoulders above the rest through this section of Melbourne's Albert Park circuit in practice one.

Daniil Kvyat.

The young Russian endured a rough time when he graduated from Toro Rosso to Red Bull as the rookie sensation of 2014.

He broke Red Bull's only front wing on his first day of pre-season testing at Jerez in 2015 and had to drive the car wingless for the rest of the day, and he found it tough to cope with struggling to beat the rookie drivers at his old team as Red Bull battled to get the RB11 working properly over the first half of last year.

But Red Bull believes Kvyat is a special talent, and he came on strong as the car improved over the second half of the season. He was fortunate to finish ahead of the highly rated Ricciardo in the championship, but finish ahead he nevertheless did.

Team boss Christian Horner has spoken before of Kvyat's extraordinary bravery and enormous commitment at high speed. This commitment was evident again, but what really impressed was the control.

The speed he carried looked impossible to maintain without a lock-up, missed apex or even a crash, but he managed it without so much as a squeal of protest from his Pirelli tyres.

Hamilton ultimately topped the timesheet in both sessions. Par for the course for Mercedes really, and the world champion looked impressively fast through this section too, but he almost went off twice and his F1 W07 did not display quite the same poise of Kvyat's RB12.

Those who braved the conditions couldn't seem to live with Kvyat. He looked a genuine superstar.

Ricciardo is a superb benchmark for his team-mate, having won three grands prix and beaten four-time world champion Sebastian Vettel across a season in the same team, but the Australian was slower than Kvyat in first practice and beached his car in the gravel as well.

Ricciardo redeemed himself by going third quickest in the wet-but-slowly-drying conditions of afternoon practice on the intermediate tyre. Kvyat looked fast at the start of this session as well, before Rosberg smacked the wall at Turn 7 and crunched his F1 W07's front wing, forcing Kvyat to back off while on a hot lap.

After the Russian returned to the pits, we were briefly treated to the rare sight of a McLaren-Honda topping the times. Has that ever happened in the V6 hybrid turbo era?

Alonso gradually worked down to a 1m39.895s best over three consecutive laps, which was bettered only narrowly by Ferrari's Kimi Raikkonen and the Toro Rosso of Alonso's Spanish protege Sainz in similar conditions.

Alonso eventually fell to sixth as others improved their times on a drier circuit later on, but both McLarens were fast enough to make the top eight in each session.

There is still much work to do, but that represents a significantly better start than this reformed alliance managed 12 months ago, when concussion sidelined Alonso from the first race and the car performed disastrously.

The new MP4-31 was tricky to drive during the final week of testing, thanks to certain aerodynamic parts not being ready in time, but it looks in much better shape here.

The low-traction conditions also mitigate for a lack of power, which is clearly helping McLaren and Red Bull be more competitive. They will slip back if the track dries out. To what extent depends on how well the Mercedes and Ferrari customer squads get their respective acts together.

Wet weather is always fascinating for drawing distinctions between the way different cars behave and how various drivers approach their craft, and a brief period of wet running on Friday morning also allowed me to observe the stark contrast between Button and Toro Rosso sophomore Verstappen.

As you'd expect, Button was all about gradual inputs, smoothness and elegance; Verstappen appeared a kid in a hurry - sharp braking, fast downshifts and squirms of oversteer as he impatiently reapplied the throttle.

Great to watch, though Verstappen later said he was still leaving plenty of margin for error. In fact he decided to sit out second practice entirely to protect his car, once he realised the circuit wasn't going to dry out.

It's a shame we didn't get to see what he could do. The Dutch teenager is clearly a star in the making, and will be hopeful of a strong result in dry conditions with 2015 Ferrari power in the back of his Toro Rosso.

It's also impossible to ignore his team-mate Sainz. He can be wild at times, but he was back on the case after sitting out most of FP1 and showed his class in second practice with a very quick time in the wet early stages, ending up third in a group including Raikkonen, Ricciardo and Alonso that led the way after the first hour.

The track was improving all the time, but these drivers and Button (only a tenth behind Alonso) showed their class and ability to read grip in changing conditions.

Force India's Nico Hulkenberg also impressed in both sessions, in a car that looked very drivable and agile in the tricky conditions. He was among the more committed drivers approaching Turn 6 in practice one, ending up fourth quickest, and only Hamilton outpaced Hulkenberg's VJM09 later on.

The team really struggled for speed using an updated version of its 2014 car here last year, but it doesn't look like Hulkenberg and Perez will face anything like the same degree of difficulty this time around.

What a difference a year makes. Though not for Mercedes, which still looks as ominously fast as ever - at least in Hamilton's hands.

Rosberg apologised for the error that made him the undoubted zero of the second session, and he now has his work cut out for the rest of the weekend.

The saving grace is that Friday's running was limited across the board, which means Rosberg shouldn't suffer as much as he otherwise would.

He will take comfort from the fact that Saturday is a new day, and a chance for new stars to shine.