NASA is considering approving by next April up to two planetary science missions from four proposals under review, including one to Venus that scientists involved in the project said could help determine whether or not that planet harbors life.

An international research team on Monday described evidence of potential microbes residing in the harshly acidic Venusian clouds: traces of phosphine, a gas that on Earth is produced by bacteria inhabiting oxygen-free environments. It provided strong potential evidence of life beyond Earth.

The U.S. space agency in February shortlisted four proposed missions that are now being reviewed by a NASA panel, two of which would involve robotic probes to Venus. One of those, called DAVINCI+, would send a probe into the Venusian atmosphere.