Mesosphere is based on Apache Mesos, Marathon and other technologies. Mesos is an abstraction of the underlying hardware - exposing APIs to allow running tasks in a cluster ~ think of just launching threads on your linux box - with Mesos it's similar, you can launch processes on your servers across your datacenter or cloud. It's production software that powers Twitter, Airbnb and other companies at scale. Mesos is more than just orchestration - it's really a fabric for writing distributed systems. Apache Spark was a sample app written for Mesos. Marathon is another application that runs on top of Mesos and orchestrates containers. It can handle tens of thousands of containers and more in a single cluster. Chronos and Storm are other systems that can run on top of Mesos.
Marathon: https://mesosphere.github.io/marathon/ Chronos: https://airbnb.github.io/chronos/