former deputy administrator at nasa, lori garver, thank you for being with us.will be watching and continue to cover the race to space. twitter ceo dick costolo is selling off more of his shares in his family trust. the third major sale in a month. what does it say about twitter's business, if anything? ♪ >> i'm emily chang. this is "bloomberg west." family trust belonging to twitter ceo dick costolo and his wife continued to unload shares. they sold off half of the remaining stake in twitter, selling 140,000 shares, this after they sold off 283,000 last month. so what does this mean? cory johnson has more. she would be concerned or curious about it? >> i am certainly curious. on the one hand, a pernicious side of you says, here is somebody telling you to buy shares in the company but he has unloaded 75% of his stock in the last four weeks. that looks worrisome if you are a shareholder, perhaps. although there are lots of reasons to sell, only one to buy. >> mark zuckerberg cells facebook shares, marc benioff selling salesforce shares. they save for tax reasons.

. >> former deputy administrator at nasa, lori garver. thank you for sharing your thoughts with us. be watching and continuing to cover this race to space. dick costolo is selling off more of his shares. it is the third major sale in a month. what does it say about twitter's business? watch us streaming on your tablet, phone, bloomberg.com, apple tv, and amazon fire tv. ♪ >> i'm emily chang. family trusts belonging to the twitter ceo and his wife continued to unload twitter shares. the trust just sold off half its or meaning stake in twitter, selling about 141,000 shares. this coming after the trust sold shares last month. what does it mean? cory johnson joins us with more. should we be concerned or curious about this? >> i'm certainly curious about it. on one hand, here's a guy who's telling us to buy twitter stock and how good things are at the company and he has unloaded 75% of his stock in the last four weeks. that looks worrisome if you are a twitter shareholder. the old saying on wall street is there's lots of reasons to sell, only one reason to buy. >> marc benioff sells shar

former nasa deputy administrator lori garver was one of the leading proponents of the original obamace plan. >> if you were driving to mars, there were a number of things you'd be doing that we're not doing now that are the difficult things. you wouldn't be building a spacecraft now based on technology from 40 years ago, engines from 40 years ago to go somewhere in 20 years and spending $3 to $4 billion a year on that. >> garver believes nasa's current path to mars is a hybrid of ideas borne not of engineering elegance but political compromise. >> the purpose has become political and jobs, and i think we're... we've lost the sort of unifying view that exploration is something that we do as a species. we should have that broader purpose rather than just a political needs of a few members of congress with jobs in their district. >> senator shelby rejects the notion that space exploration has become a jobs program. >> well, i'd be against a jobs program. i'm for the cutting-edge of space. jobs come with it if you've got a good system that you're building. i believe this will be a good s