"approved by an outside panel"
Actually the "outside" panel was CERN's Scientific Policy Committee. Similar to a company's board of directors. So calling it an outside panel is a bit of a stretch.
In order for Earth to be in danger based on current assumptions, the following would need to be true:
- Micro black holes would need to be creatable at collider energies. This is unknown, but reasonably plausible according to the CERN Courier and CERNs public safety web site.
- Micro black holes would need to be stable and not decay. This is unknown, most physicists predict decay, though several PHDs of Math and Physics argue that decay is an open question.
- Micro black holes would need to grow quickly. This is also unknown, Dr. Otto Rossler theorizes that a micro black hole could become charged by capturing electrons "in orbit" outside its event horizon. 2008 LSAG Safety Report also accepts that if micro black holes were charged they would likely grow quickly.
The probability of danger is unknown, the legal action currently before US Federal Courts estimates high risk and cosmic ray impacts with Earth do not prove safety because results of cosmic rays pass through Earth and into space at nearly the speed of light. If colliders create micro black holes from head-on collisions, some percentage will travel too slowly to escape Earth's gravity.
Wikipedia, Safety of the Large Hadron Collider
LHCFacts.org
LHCDefense.org