April 20 (UPI) -- Celebrity couples stepped out to celebrate scientists at this year's Breakthrough Prize ceremony. Maroon 5 singer Adam Levine and model Behati Prinsloo , singer Christina Aguilera and Matthew Rutler, actress Zoe Saldana and Marco Perego, and socialite Paris Hilton and Carter Reum walked the red carpet Saturday in Santa Monica, Calif. Actor Robert Downey Jr. and producer Susan Downey , actress Salma Hayek and businessman Francois-Henri Pinault , model Miranda Kerr and Reddit co-