Signs of plumes spotted more than a decade ago have disappeared with more data
Signs of plumes of water spewing from Jupiter’s icy moon Europa have disappeared into a haze of hydrogen.
An analysis of nearly a decade of observations of Europa by the Hubble Space Telescope shows no solid evidence of steam jets that were claimed 13 years ago, researchers report in May report Astronomy and astrophysics.
“They disappeared,” says planetary astronomer Lorenz Roth of the KTH Royal Institute of Technology in Stockholm. “I don’t think there’s any solid evidence left.” This disappearing act could have implications for the search for life in Europe’s underground sea.
Roth and his colleagues caused a stir in 2013 when they reported excess ultraviolet light coming from hydrogen and oxygen atoms. hovering around the south pole of Europe. Evidence at the time suggested that cracks in Europa’s icy surface intermittently opened and let water from the Moon’s interior ocean escape into space.
Europa’s ocean makes it one of the best places to search for life in the solar system. But its ice shell several kilometers thick makes the ocean difficult to study. The plumes could allow a spacecraft to collect a sample simply by hovering over it, without having to land or drill.
Roth and his colleagues observed Europa with Hubble again and again. The first time, “I said to myself: We know where and when he is now, we’ll see him again,” Roth says. “And we didn’t.”
In the new study, Roth and his colleagues analyzed 20 Hubble observations taken between 2013 and 2020, plus three – two in 2012 and one in 1999 – that led to the original study. In ultraviolet, Europa looks like a fuzzy ball of TV static, even to the sharp-eyed Hubble. The new analysis included improved methods to constrain the location of Europa’s edges, as shifting just a pixel or two could change the result. The team also included new knowledge about Europa over the past 13 years, such as that it has a vast hydrogen exosphere that Hubble can detect.
The excess ultraviolet from Europe has disappeared.
The original plume or other smaller ones could still be there, undetected by Hubble, Roth says. from NASA Europa Clipper spaceship will be able to check when it arrives on Jupiter in April 2030.
“I’m excited that Europa Clipper has the ability and instruments to find smaller things,” says Roth. “But I’m not too optimistic that we’ll find evidence before Europa Clipper. We still have four years of not knowing.”