The 2015 Formula 1 season gets underway this weekend with the first race in a 20-grands prix season, the Australian Grand Prix in Melbourne.

Mercedes's Lewis Hamilton starts as the pre-season favourite to retain his world title, with the German team having posted the fastest times in testing.

However, teammate Nico Rosberg got the better of him in the first two practice sessions at Albert Park earlier.

Sports Mole takes a look at some of the talking points that have dominated the winter break.

1. Safety

The dangers of Formula 1 racing were thrust back into the spotlight with Jules Bianchi's crash at the Japanese Grand Prix last season, which resulted in a diffuse axonal injury that continues to keep him in a coma.

Following an investigation into the Frenchman's crash, a number of changes have been made for this season, including the introduction of a virtual safety car, which was trialed last season, while several races, including this weekend's and the Suzuka event where the incident occurred, will now be held one hour earlier.

There have been further safety concerns following Fernando Alonso's mysterious pre-season testing crash in Barcelona, which has forced the two-time world champion to sit out this weekend's race.

The Spaniard had to be airlifted from the Circuit de Catalunya following the collision, and has admitted to suffering memory loss following the incident, believing that it was 1995 after regaining consciousness.

McLaren, who are running both of their cars in Melbourne with reserve driver Kevin Magnussen filling in for Alonso, are still looking into what caused the crash, but have given assurances that the car is safe.

2. Pay drivers

The concept of a driver using sponsorship to fund their seat with an F1 team certainly is not something new for 2015, but it has been making headlines in the last couple of weeks, with Giedo van der Garde taking Sauber to court to secure a place with the team.

The Dutchman signed a contract for this season midway through the last campaign, but was told that he would not be needed after the highly-sponsored Marcus Ericsson and Filipe Nasr were signed up by the Swiss side.

Courts in Switzerland and Australia both ruled in favour of the driver, but that now leaves the team with three contracted drivers for two race seats, with the constructor admitting that they need the funds provided by Ericsson and Nasr to operate.

Van der Garde was at the track this morning, but could not drive as he needs to wait for his licence to be approved.

Sauber are not the only team with so-called pay drivers though, as the reborn Manor F1 team, which replaces Marussia, chose to sign former Caterham test driver Robert Mehri, who has not taken part in a grand prix before, to a one-race deal, while more experienced drivers like Kamui Kobayashi and Max Chilton head to other racing series.

3. The 17-year-old F1 driver

Toro Rosso new boy Max Verstappen will become the youngest ever F1 driver this weekend when he lines up on the grid on Sunday at the age of 17.

It is a record that will not be broken for the foreseeable future, as the FIA has changed its rules since the Dutch youngster was signed by the team, meaning that drivers must now be 18 to apply for a Super Licence.

He comes from a racing family, with father Jos Verstappen having also competed in F1, while his mother was a two-time Belgian karting champion. He made his own debut in a kart at just four years old.

Verstappen certainly showed that he had talent last season as he finished third in the European Formula 3 championship, and also had good pace in last season's Toro Rosso in practice at the Japanese Grand Prix.

He has another rookie opposite him in the garage as Carlos Sainz Jr replaced Jean-Eric Vergne in the Italian team, and was sixth fastest in first practice earlier, just behind four-time world champion Sebastian Vettel.

4. Mercedes's dominance

With few changes to the technical specifications of this year's cars, many are expecting another season dominated by the Mercedes team, with Lewis Hamilton and Nico Rosberg having done little to suggest otherwise so far.

However, it does appear that the gap to the German manufacturer has closed, with Williams and Toro Rosso both pushing them in practice.

It also looks like some of the other teams have made big leaps forward from last year, with Ferrari and Lotus looking much more competitive and reliable so far.

Red Bull were the only other team to win a race last season, with Daniel Ricciardo claiming three victories in his first campaign with the Austrian outfit, but reliability issues have limited their running time so far, so it is not yet known whether they will be able to push Mercedes again.

So far though, it does not look like one team has the consistency, pace and reliability to really push the Silver Arrows in the early races.

5. German Grand Prix

Currently, 20 races are scheduled for this season, with the Mexican Grand Prix making its first appearance since 1992 - good news for Force India's Sergio Perez, as he will get to race in his home country in an F1 car for the first time.

There could be bad news for the three German drivers on the grid though, as there are doubts over whether their race will go ahead this year.

The German Grand Prix currently alternates between the Hockenheimring and the Nurburgring so that each venue does not have to pay to hold the event once a year, with the latter due to play host this season.

F1 boss Bernie Ecclestone has admitted that he does not know whether this season's race will be able to go ahead though, with dwindling attendances leading to questions over the economic viability of the event.

Last year's race, which was won by Germany's Nico Rosberg, pulled in just 52,000 spectators, compared with the 120,000 who watched Lewis Hamilton win his home race at Silverstone just two weeks earlier.

For the time being, the race is still scheduled to go ahead on July 19, but it remains to be seen whether it will be at the Nurburgring, and if not whether Hockenheim will host it instead.