Hershey Co. and Mars Inc. said their Bliss and Dove lines, respectively, are marketed toward women.

WSJ: Hoppy Holidays: Sweet Makers

Mars Inc. and Raytheon Co.

WSJ: Fine-Tuning the Perfect Employee

"It happened probably right at the end of the formation of the four terrestrial planets - Mercury, Venus, Earth and Mars, " said Craig Agnor, a co-author on the Francis Nimmo study.

BBC: Mars' two-faced riddle 'solved'