martes, 27 de septiembre de 2016

00:11:00
BARCELONA / MADRID, 27 de septiembre.- La agencia espacial americana anunció ayer el descubrimiento de un océano subterráneo en Europa, una de las lunas de Júpiter. La NASA ya había explicado previamente que existían “indicaciones sorprendentes de actividad” en Europa, lo que podría suponer que se diesen las condiciones propicias para la existencia de vida. “Hemos localizado posibles emisiones de vapor que manan de la luna Europa de Júpiter usando el telescopio espacial Hubble”, afirmó la NASA en un comunicado.

El hallazgo aumenta la posibilidad de que las misiones enviadas a Europa en un futuro puedan analizar el océano de la luna helada sin necesidad de perforar kilómetros de hielo.

Según ha explicado la NASA, existen evidencias de que desde el satélite son expulsadas plumas de agua (chorros similares a géiseres) hacia el espacio. Gracias a Hubble se ha podido dar constancia de pistas de un océano subterráneo de agua que en un futuro próximo, podría explorarse para buscar moléculas orgánicas o evidencias de vida. Los hallazgos se hicieron analizando la luz ultravioleta.


Los astrobiólogos consideran Europa como una de las mejores apuestas en el sistema solar para albergar vida extraterrestre. La luna de 3.100 kilómetros alberga un enorme océano con dos veces el agua de todos los océanos de la Tierra, si bien el líquido está protegido por una capa de hielo de grosor desconocido. Por otra parte, los astrónomos piensan que este océano está en contacto con el manto rocoso de Europa, lo que hace posible todo tipo de reacciones químicas interesantes.

En diciembre de 2012, Hubble detectó lo que parecían ser plumas de vapor extendiéndose unos 200 kilómetros hacia el espacio desde la superficie del polo sur de Europa, observación que no había podido ser confirmada hasta ahora.

Los científicos de la NASA, liderado por William Sparks, del Instituto de Ciencia Telescópica Espacial (STScI, en sus siglas en inglés), con sede en Baltimore (EE.UU.), captaron las emisiones mientras observaban una extremo de la luna al pasar delante de Júpiter.


El objetivo original del equipo de Sparks era determinar si Europa tiene una atmósfera delgada o una exófera que podría bloquear luz desprendida por Júpiter.

El estudio de la NASA refuerza la posibilidad de emisiones de vapor de agua en Europa, después de que en 2012 un equipo del Instituto de Investigación Southwest, en San Antonio (EE.UU.), detectara evidencias de vapor de agua que salían de la región polar meridional de Europa y alcanzaron una altitud de más de 160 kilómetros.

Los dos equipos de investigadores utilizaron el telescopio Hubble, pero emplearon métodos diferentes para llegar a la misma conclusión.

Sparks subrayó hoy que las “estimaciones” de la altitud de las emisiones y de la latitud de dos de ellas son similares a las obtenidas por los expertos de San Antonio.

Si se confirma el descubrimiento anunciado hoy, Europa sería la segunda luna del sistema solar conocida por tener emisiones de vapor de agua.

En 2005, la nave internacional Cassini, de la NASA, detectó chorros de vapor de agua y polvo sobre la superficie de la luna Enceladus, del planeta Saturno, informan La vanguardia en su sección Big Vang y El País.

NASA’s Hubble Spots Possible Water Plumes Erupting on Jupiter's Moon Europa

(NASA / Sept.26,2016 Release 16-096)

Astronomers using NASA's Hubble Space Telescope have imaged what may be water vapor plumes erupting off the surface of Jupiter's moon Europa. This finding bolsters other Hubble observations suggesting the icy moon erupts with high altitude water vapor plumes.

The observation increases the possibility that missions to Europa may be able to sample Europa’s ocean without having to drill through miles of ice.

“Europa’s ocean is considered to be one of the most promising places that could potentially harbor life in the solar system,” said Geoff Yoder, acting associate administrator for NASA’s Science Mission Directorate in Washington. “These plumes, if they do indeed exist, may provide another way to sample Europa’s subsurface.”

The plumes are estimated to rise about 125 miles (200 kilometers) before, presumably, raining material back down onto Europa's surface. Europa has a huge global ocean containing twice as much water as Earth’s oceans, but it is protected by a layer of extremely cold and hard ice of unknown thickness. The plumes provide a tantalizing opportunity to gather samples originating from under the surface without having to land or drill through the ice.

The team, led by William Sparks of the Space Telescope Science Institute (STScI) in Baltimore observed these finger-like projections while viewing Europa's limb as the moon passed in front of Jupiter.

The original goal of the team's observing proposal was to determine whether Europa has a thin, extended atmosphere, or exosphere. Using the same observing method that detects atmospheres around planets orbiting other stars, the team realized if there was water vapor venting from Europa’s surface, this observation would be an excellent way to see it.

"The atmosphere of an extrasolar planet blocks some of the starlight that is behind it," Sparks explained. "If there is a thin atmosphere around Europa, it has the potential to block some of the light of Jupiter, and we could see it as a silhouette. And so we were looking for absorption features around the limb of Europa as it transited the smooth face of Jupiter."

In 10 separate occurrences spanning 15 months, the team observed Europa passing in front of Jupiter. They saw what could be plumes erupting on three of these occasions.

This work provides supporting evidence for water plumes on Europa. In 2012, a team led by Lorenz Roth of the Southwest Research Institute in San Antonio, detected evidence of water vapor erupting from the frigid south polar region of Europa and reaching more than 100 miles (160 kilometers) into space. Although both teams used Hubble's Space Telescope Imaging Spectrograph instrument, each used a totally independent method to arrive at the same conclusion.

"When we calculate in a completely different way the amount of material that would be needed to create these absorption features, it's pretty similar to what Roth and his team found," Sparks said. "The estimates for the mass are similar, the estimates for the height of the plumes are similar. The latitude of two of the plume candidates we see corresponds to their earlier work."

But as of yet, the two teams have not simultaneously detected the plumes using their independent techniques. Observations thus far have suggested the plumes could be highly variable, meaning that they may sporadically erupt for some time and then die down. For example, observations by Roth’s team within a week of one of the detections by Sparks’ team failed to detect any plumes.

If confirmed, Europa would be the second moon in the solar system known to have water vapor plumes. In 2005, NASA's Cassini orbiter detected jets of water vapor and dust spewing off the surface of Saturn's moon Enceladus.

Scientists may use the infrared vision of NASA’s James Webb Space Telescope, which is scheduled to launch in 2018, to confirm venting or plume activity on Europa. NASA also is formulating a mission to Europa with a payload that could confirm the presence of plumes and study them from close range during multiple flybys.

“Hubble’s unique capabilities enabled it to capture these plumes, once again demonstrating Hubble’s ability to make observations it was never designed to make,” said Paul Hertz, director of the Astrophysics Division at NASA Headquarters in Washington. “This observation opens up a world of possibilities, and we look forward to future missions -- such as the James Webb Space Telescope -- to follow up on this exciting discovery.”

The work by Sparks and his colleagues will be published in the Sept. 29 issue of the Astrophysical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (the European Space Agency.) NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. STScI, which is operated for NASA by the Association of Universities for Research in Astronomy in Washington, conducts Hubble science operations.