The conference's details remain a secret -- Amazon hasn't even confirmed it yet. But Bloomberg says the guests attended seminars, including one that talked about giving robots human values. iRobot co-founder Helen Greiner also tweeted that she went to the conference, saw "old roboticist friends" and met new ones.

Seeing old roboticist friends and meeting new cool machine intelligence and space people @ MARS conference sponsored by @amazon — Helen Greiner (@helengreiner) March 21, 2016

Amazon focused on these particular fields, most likely because they're all relevant to its interests. It has robots working in its warehouses, and it even held a robotics challenge last year to develop machines that can find items and fulfill orders. Its Amazon Echo speakers come with Alexa, its voice assistant that can read ebooks aloud, control the lights and give you election updates. Finally, Jeff Bezos is in personally invested in the future of space exploration as Blue Origin's founder and backer.