How many senior scientists — usually men and usually with significant power over the careers of those in their labs — have been sanctioned and disciplined by their universities for sexual harassment? Nobody knows, especially not young researchers who eagerly apply for their first jobs, spend long hours on fieldwork and feel under pressure to socialize and make contacts after hours and at academic conferences. How many times have colleagues turned a blind eye to inappropriate comments and actions, and made excuses for people who should know better — and who are morally, legally and contractually obliged to behave better? How many young scientists have left positions, or left science completely, because of such behaviour, or because it is seemingly not taken seriously?

We don’t know the answers to those questions. But one thing we do know is that sexual harassment is a serious problem in science. And we know that young female scientists are speaking up about it. We know this not because universities are being transparent about such complaints and how they are dealt with, but because, dissatisfied with the official responses, victims, journalists and others are bringing the facts about these complaints to light.

In a World View this week, for example, Nature publishes the testimony of a female researcher who was persistently harassed by a senior male colleague. His university investigated and upheld her complaint. But it told her to keep the matter confidential, and although it promised action against him, allowed the offender to stay in his post. Nature knows who he is, but in this case, the female researcher did not want to name him for fear of reprisals.

Apologists for sexual harassment will tell you that it ‘is rarely a black and white issue’ and that inappropriate behaviour often ‘falls into a grey area’. Read this woman’s story: having an influential male colleague 30 years your senior ask to stay at your house for a work trip, request kisses and then enquire whether his night-time masturbation kept you awake is 100% wrong.

Nature and others have encouraged scientists to stand up to such behaviour. But it is clear that the system is weighted towards protecting powerful faculty members at the expense of students and young researchers. Although institutions proclaim that they have zero tolerance for abuse of the policies that they claim to enforce, too often their primary concern seems to be secrecy and reputation management.

A string of cases in the US astronomy community demonstrates this. In each, a university investigated sexual-harassment claims against a faculty member, found the claims substantiated and attempted to bury that fact from public view.

Any principal investigator who thinks, ‘It cannot happen at my university,’ is wrong.

The latest disclosures, made public last week, revealed that astrophysicist Christian Ott of the California Institute of Technology (Caltech) in Pasadena was suspended without pay last year for harassing two female graduate students. And Congresswoman Jackie Speier (Democrat, California) took the extraordinary step of decrying sexual harassment in science on the floor of the US House of Representatives. She entered into the Congressional Record a 2005 University of Arizona finding of harassment regarding Timothy Slater, an astronomy educator who later moved to the University of Wyoming in Laramie.

These incidents follow probably the most high-profile recent case, which saw exoplanet hunter Geoffrey Marcy leave the University of California, Berkeley, late last year, but only after complaints and a university finding against him were revealed by news media.

Scientists accused of such behaviour have the right to have their identities protected unless and until the claims are proved. But once an investigation has been completed and signed off, it is incumbent on those in power to be sure that they act on it. Disciplinary action is a good first step; ensuring that the victims have a path forward in science is another.

There have been baby steps in the right direction, such as the effort by US President Barack Obama’s administration to make it clearer to students what their rights are and how they can go about reporting a sexual violation. And Speier is working to force the US Department of Education to make sure that when a person found to have violated the law changes institutions, all institutions involved are aware of the situation.

Any principal investigator who thinks, “It cannot happen at my university,” is wrong. These are not one-off cases. They are examples of a systemic underlying rot that is driving many young researchers out of science for good.