Mercury is a Waves-powered provenance token. It enables collaborative cross-chain communication and timestamping from the Jupiter blockchain to Waves and Waves to Jupiter. The reason Waves was chosen to build the Mercury token on, is because the Waves blockchain allows for transactions fees to be paid in the asset itself.
The first use case of Mercury is automatically timestamping every Jupiter block hash to the Waves blockchain. By copying block hashes of the private blockchain to the public one, there is undeniable public proof that nobody tampered with the data of the private blockchain.
As more and more Waves nodes are accepting Mercury, we now have a fully functional token in the Waves ecosystem and this opens the door for all kinds of new possibilities.