NASA en español : El Océano de Europa Podría Tener un Equilibrio Químico Como el de la Tierra

https://www.lanasa.net/news/newsnasa/el-oceano-de-europa-podria-tener-un-equilibrio-quimico-como-el-de-la-tierra/



18.05.16.- Un nuevo estudio de la NASA sugiere que el océano bajo la superficie helada de la luna Europa de Júpiter tendría el necesario equilibrio de energía química para que la vida pudiera existir allí, incluso sin actividad hidrotermal volcánica.

Se tiene el convencimiento de que Europa esconde un profundo océano de agua líquida salada debajo de su corteza helada. Si la luna joviana tiene las materias primas y la energía química en las proporciones adecuadas para apoyar la biología es un tema de interés científico. La respuesta puede depender de si Europa dispone de entornos en los que los productos químicos se cotejan en las proporciones adecuadas para alimentar los procesos biológicos. La vida en la Tierra explota dichos nichos.

En un nuevo estudio, los científicos del Laboratorio de Propulsión a Chorro de la NASA en Pasadena, California, compararon el potencial de Europa para la producción de hidrógeno y oxígeno el la de la Tierra, a través de procesos que no implican directamente el vulcanismo. El equilibrio de estos dos elementos es un indicador clave de la energía disponible para la vida. El estudio encontró que las cantidades serían comparables en escala; en ambos mundos, la producción de oxígeno es aproximadamente 10 veces mayor que la producción de hidrógeno.

El trabajo llama la atención sobre las formas en que el interior rocoso de Europa puede ser mucho más complejo y posiblemente parecido a la Tierra de lo que se suele pensar, según Steve Vance, científico planetario del JPL y autor principal del estudio. "Estamos estudiando un océano extraterrestre utilizando métodos desarrollados para comprender el movimiento de la energía y los nutrientes en los sistemas propios de la Tierra. El ciclo del oxígeno y el hidrógeno en el océano de Europa sería un factor importante para la química de ese océano y toda la vida allí, tal como lo es en la Tierra".

En última instancia, Vance y sus colegas quieren entender también el ciclo de los otros elementos importantes de la vida en el océano: carbono, nitrógeno, fósforo y azufre.

Como parte de su estudio, los investigadores calcularon la cantidad de hidrógeno que podría producirse en el océano de Europa a medida que el agua de mar reacciona con la roca, en un proceso llamado serpentinización. En este proceso, el agua se filtra en los espacios entre granos minerales y reacciona con la roca para formar nuevos minerales, liberando hidrógeno en el proceso. Los investigadores examinaron cómo se abrirían las grietas en el fondo marino de Europa, mientras el interior rocoso de la luna sigue enfriándose tras miles de millones de años de formación. Nuevas grietas exponen roca fresca al agua de mar, donde más reacciones que producen hidrógeno pueden tener lugar.

 

Esta imagen en color realzado de la nave espacial Galileo de NASA muestra un complicado patrón de fracturas lineales sobre la superficie helada de la luna Europa de Júpiter.
Image Credit: NASA/JPL-Caltech/SETI Institute

 

En la corteza oceánica de la Tierra, se cree que este tipo de fracturas penetra a una profundidad de 5 a 6 kilómetros. En la actual Europa, los investigadores esperan que el agua podría llegar a una profundidad de 25 kilómetros en el interior rocoso, propiciando estas reacciones químicas clave a lo largo de una fracción más profunda de fondo marino de Europa.

La otra mitad de la ecuación química de Europa de vida a través de la energía química estaría a cargo de los oxidantes - oxígeno y otros compuestos que puedan reaccionar con el hidrógeno - siendo sometidos a ciclos en el océano de Europa desde la superficie helada anteriormente. Europa está bañado por la radiación de Júpiter, que divide las moléculas de hielo de agua para crear estos materiales. Los científicos han deducido que la superficie de Europa se cicla de nuevo en su interior, lo que podría llevar a los oxidantes al océano.

"Los oxidantes del hielo son como el terminal positivo de la batería, y los productos químicos desde el fondo del mar, llamados reductores, son como el terminal negativo. Sea o no la vida y los procesos biológicos lo que completa el circuito es parte de lo que motiva nuestra exploración de Europa ", dijo Kevin Hand, científico planetario del JPL, y co-autor del estudio.

La rocosa luna joviana vecina de Europa, Io, es el cuerpo con mayor actividad volcánica en el sistema solar, debido al calor producido por el estiramiento y los efectos de la gravedad de Júpiter a medida que orbita el planeta. Los científicos han considerado durante mucho tiempo que es posible que Europa también pueda tener actividad volcánica, así como fuentes hidrotermales, donde el agua caliente cargada de minerales emergería del fondo del mar.

Según Vance, los investigadores especularon con anterioridad que el vulcanismo es de suma importancia para la creación de un entorno habitable en el océano de Europa. Si dicha actividad no está ocurriendo en su interior rocoso, según se piensa, el gran flujo de oxidantes de la superficie del océano sería demasiado ácido y tóxico para la vida. "Pero en realidad, si la roca es fría, es más fácil que se fracture. Esto permite que una enorme cantidad de hidrógeno que se produce por serpentinización equilibre los oxidantes en una proporción comparable a la de los océanos de la Tierra", concluyó Vance.

NASA en español
Guillermo Gonzalo Sánchez Achutegui
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NASA : Scientists Find Evidence of ‘Diving’ Tectonic Plates on Jupiter’s Moon Europa

Scientists have found evidence of plate tectonics on Jupiter’s moon Europa. This conceptual illustration of the subduction process (where one plate is forced under another) shows how a cold, brittle, outer portion of Europa’s 20-30 kilometer (roughly 10-20 mile) thick ice shell moved into the warmer shell interior and was ultimately subsumed. A low-relief subsumption band was created at the surface in the overriding plate, alongside which cryolavas may have erupted.

Image Credit: 

Noah Kroese, I.NK

Scientists have found evidence of plate tectonics on Jupiter’s moon Europa. This indicates the first sign of this type of surface-shifting geological activity on a world other than Earth.

Researchers have clear visual evidence of Europa’s icy crust expanding. However, they could not find areas where the old crust was destroyed to make room for the new.  While examining Europa images taken by NASA’s Galileo orbiter in the early 2000s, planetary geologists Simon Kattenhorn, of the University of Idaho, Moscow, and Louise Prockter, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, discovered some unusual geological boundaries.

“We have been puzzled for years as to how all this new terrain could be formed, but we couldn’t figure out how it was accommodated,” said Prockter. “We finally think we’ve found the answer.”

Plate tectonics is the scientific theory that Earth's outer layer is made up of plates or blocks that move, which accounts for why mountain and volcanoes form and earthquakes happen.

The surface of Europa -- one of Jupiter’s four largest moons and slightly smaller than Earth’s moon -- is riddled with cracks and ridges. Surface blocks are known to have shifted in the same way blocks of Earth's outer ground layer on either side of the San Andreas fault move past each in California. Many parts of Europa’s surface show evidence of extension, where wide bands miles wide formed as the surface ripped apart and fresh icy material from the underlying shell moved into the newly created gap -- a process akin to seafloor spreading on Earth.

On Earth, as new surface material forms at mid-ocean ridges, old material is destroyed at subduction zones, which are regions where two tectonic plates converge and overlap as one is forced under the other. However, despite the degree of extension evident on Europa’s surface, researchers had not been able to determine how the surface could accommodate all the new material.

Scientists studying Europa often reconstruct the moon’s surface blocks into their original configuration -- as with a jigsaw puzzle -- to get a picture of what the surface looked like before the disruption occurred. When Kattenhorn and Prockter rearranged the icy terrain in the images, they discovered about 7,700 square miles (about 20,000 square kilometers) of the surface were missing in the moon’s high northern latitudes.

Further evidence suggested the missing terrain moved under a second surface plate -- a scenario commonly seen on Earth at plate-tectonic boundaries. Kattenhorn and Prockter saw ice volcanoes on the overriding plate, possibly formed through melting and absorption of the slab as it dove below the surface, and a lack of mountains at the subduction zone, implying material was pushed into the interior rather than crumpled up as the two plates mashed against each other.

The scientists believe the subducted area was absorbed into Europa's ice shell, which may be up to 20 miles (about 30 kilometers) thick, rather than breaking through it into Europa's underlying ocean. On Europa’s relatively young surface -- about 40-90 million years old, on average -- scientists have seen evidence of material moving up from under the shell but, until now, no mechanism had been found for moving material back into the shell, and possibly into the large ocean below the ice.

“Europa may be more Earth-like than we imagined, if it has a global plate tectonic system,” Kattenhorn says. “Not only does this discovery make it one of the most geologically interesting bodies in the solar system, it also implies two-way communication between the exterior and interior -- a way to move material from the surface into the ocean -- a process which has significant implications for Europa’s potential as a habitable world.”

The team’s results appear in the Sunday online edition of the journal Nature Geoscience.

In July, NASA issued an Announcement of Opportunity (AO) for proposals for science instruments that could be carried aboard a future mission to Europa.

“Europa continues to reveal itself as a dynamic world with compelling similarities to our own planet Earth,” said Curt Niebur, Outer Planets program scientist at NASA Headquarters in Washington. “Studying Europa addresses fundamental questions about this potentially habitable icy moon and the search for life beyond Earth.”

Previous scientific findings point to the existence of a liquid water ocean located under the moon’s icy crust. This ocean covers Europa entirely and contains more liquid water than all of Earth's oceans combined.

NASA’s Galileo spacecraft, launched in 1989, was the only space mission to make repeated visits to Europa, passing close by the moon about a dozen times.

Galileo’s many firsts include discovering evidence for the existence of a saltwater ocean beneath Europa's icy surface. The mission officially was ended when Galileo plunged into Jupiter's atmosphere in September 2003 to prevent an impact with Europa. The mission was managed by NASA’s Jet Propulsion Laboratory in Pasadena, California, for the agency’s Science Mission Directorate in Washington.

For more information about Europa and images of the plate tectonics, visit:

http://solarsystem.nasa.gov/europa

Information is available online about the Galileo Mission at:

http://www.jpl.nasa.gov/missions/galileo/

NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

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NASA: NASA Seeks Proposals for Europa Mission Science Instruments

Compiled from NASA’s Galileo spacecraft data, this colorized surface image of Europa shows the blue-white terrains which indicate relatively pure water ice. Scientists are very interested in these features because they may offer a way to investigate the habitability of the moon’s interior ocean.

Image Credit: 

NASA/JPL-Caltech/SETI Institute

Feature Link: 

Full image and caption

 

 

NASA has issued an Announcement of Opportunity (AO) for proposals about science instruments that could be carried aboard a future mission to Jupiter’s moon Europa. Selected instruments could address fundamental questions about the icy moon and the search for life beyond Earth.

“The possibility of life on Europa is a motivating force for scientists and engineers around the world,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate at the agency’s headquarters in Washington. “This solicitation will select instruments which may provide a big leap in our search to answer the question: are we alone in the universe?”

NASA will first select approximately 20 proposals in April 2015. Subsequently, the agency will provide approximately $25 million for selectees to advance instrument formulation and development as part of a Phase A concept study. After detailed review of selectees' reports, agency officials will select approximately eight instruments to be built for flight and science operations.

The AO calls for proposals compatible with a spacecraft that would either orbit or perform multiple flybys of Europa. Spacecraft instruments will be used to conduct high priority scientific investigations addressing the science goals for the moon's exploration outlined in the National Resource Council’s (NRC) Planetary Decadal Survey.

The Decadal Survey deemed a mission to Europa among the highest priority scientific pursuits for NASA. It listed five key science objectives in priority order that are necessary to improve our understanding of the potentially habitable moon:
 

• Characterize the extent of the ocean and its relation to the deeper interior
• Characterize the ice shell and any subsurface water, including their heterogeneity, and the nature of surface-ice-ocean exchange
• Determine global surface, compositions and chemistry, especially as related to habitability
• Understand the formation of surface features, including sites of recent or current activity, identify and characterize candidate sites for future detailed exploration
• Understand Europa’s space environment and interaction with the magnetosphere.

While characterizing landing sites for future exploration is the fourth scientific priority in the Planetary Decadal Survey, NASA places high priority on this goal to enable a potential future lander mission to Europa. Current data does not provide sufficient information to identify landing sites and design a landing system capable of safely reaching the surface. In the AO, NASA included a reconnaissance goal to characterize scientifically compelling sites, as well as hazards, for a potential future landed mission to Europa.

“Proposals must be responsive to one or more of the six objectives," said Curt Niebur, Outer Planets Program scientist at NASA Headquarters in Washington. “Plans could be adjusted to programmatic decisions made by NASA in the future.”

Any mission to Europa must take into account the harsh radiation environment that would require unique protection of the spacecraft and instruments. In addition, spacecraft must meet planetary protection requirements intended to protect Europa’s potentially habitable ocean. These requirements are very strict and involve ensuring that a viable Earth organism is not introduced into the Europa ocean.

Previous scientific findings point to the existence of a liquid water ocean located under the moon’s icy crust. This ocean covers Europa entirely and contains more liquid water than all of Earth's oceans combined.

Although Europa and Jupiter’s other moons have been visited by other spacecraft, they were each limited to a single distant flyby. NASA’s Galileo spacecraft, launched in 1989 , was the only mission to make repeated visits to Europa, passing close by the moon less than a dozen times.

The NRC recommended NASA try to reduce the cost and scope of a mission to Europa, and the agency still is working out its plans for such an undertaking. In April, NASA released a request for information for concepts for a mission to Europa that would cost less than $1 billion, excluding the launch vehicle, which could still meet as many of the science priorities as possible. Recent NASA studies have focused on an orbiter mission concept and a multiple flyby mission concept as the most compelling and feasible.

Deadline for submitting proposals to the AO is October 17.

To view the AO in its entirety, visit:
 

http://go.nasa.gov/1p1QU0b

 

For more information about Europa, visit:

 http://solarsystem.nasa.gov/europa

 

NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@Hotmail.com

ayabaca@yahoo.com

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