Scientists, technologists, and policy experts who gathered recently at the Massachusetts Institute of Technology (MIT) are enthusiastic about the prospect of lunar and Mars missions. However, they cautioned that the path to exploration beyond Earth orbit will not be easy and will probably require significant changes at NASA and in the aerospace industry. "We can in fact do this mission inside the resources that are available," but there are several thorny issues, said Robert Walker, a former Republican Congressman from Pennsylvania who chaired the House Science Committee and also served this year on the Presidential Commission on the Implementation of...