The United States is deeply concerned about Turkey’s sentencing of a Turkish-American scientist as a member of a terrorist organisation, the U.S. State Department said in a statement.

Serkan Gölge, who worked studying the effects of radiation for the Mars programme at the Johnson Space Centre in Houston, Texas, faced 15 years imprisonment for allegedly being a member of the Fethullah Gülen movement, Turkish news site Gazete Istanbul said.

The State Department said Gölge had been convicted “without credible evidence” and that Turkey should act to “safeguard the rule of law”. It was not immediately clear however what Gölge’s sentence was.