Marine aerosols such as sea spray aerosol emitted from oceans constitute the most globally abundant aerosol type by mass and can serve as ice nuclei. Ice formation can proceed via heterogeneous nucleation and homogeneous nucleation at different atmospheric conditions. Ice nucleation, which has been observed to be a dominant process in deep convective clouds or cirrus, remains a challenge in the atmosphere. Homogeneous nucleation of ice from aqueous droplets depend only on the water activity (aw) of the solution. However, data on aw for supercooled aqueous solutions are scarce. Here, we measure the melting temperature and homogenous ice nucleation for marine related aqueous droplets including methanesulfonic acid, methanesulfonte salt, and other organics. The aw of these aerosol systems will be measured or derived at temperature down to homogeneous ice nucleation limit. Possible heterogeneous ice nucleation of these aerosol systems will also discussed for better understanding on the role of these marine related particles in cloud formation