Spacemesh is a group of academia researchers and engineers set to rebuild from scratch the operating system powering an energy-efficient, decentralized, secure, and scalable smart contracts global computer and a cryptocurrency in the permissionless settings. For Blockchain revolution to have real impact on productivity growth, it must sustain equality in access to resources. The current state of the PoW mining industry fails to meet this requirement. In addition, other near-future innovations involve PoStake, which require large deposits to be staked upfront, and may thus be even worse on this front. The heart of Spacemesh OS is a new consensus protocol that replaces PoW with Proof of Space Time (PoST), and simpler chain with a mesh topology. The Spacemesh protocol allows newcomers to contribute to the security of the cryptocurrency network via unused storage space on their hard drives. PoST retains the properties of PoW that are useful for permissionless consensus, but with drastically lower energy emissions. In contrast to PoStake, the PoST mechanism enables users to participate in the system without locking any security deposit, and also avoids other nothing-at-stake problems, such as the higher risk of divergence due to hard-fork replicas.