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What's Up In Space? Witness an elusive Comet 67P outburst

Scott Sutherland
Meteorologist/Science Writer

Wednesday, April 22, 2015, 7:50 PM - NASA's MESSENGER probe coasts into its last days, a new coalition searches for life on distant worlds and witness an elusive comet outburst in action. It's What's Up In Space!

MESSENGER's Last Days Around Mercury

A little over a week from now, on April 30, 2015, the planet Mercury should have a new crater on its surface.

This isn't due to some passing asteroid, but instead will be formed as NASA's MESSENGER probe drops from orbit and smashes into the ground there.

Artists concept of MESSENGER
at Mercury. Credit: NASA

This crash-ending doesn't come as the result of some callous budget cut, or neglect from the mission team. After thousands of orbits around Mercury, and numerous course corrections to counter the Sun's gravitational efforts to push the spacecraft into the surface of the planet, MESSENGER has simply run out of fuel.

According to MESSENGER Participating Scientist Dave Blewett:

At the expected time of impact (just before midnight Eastern time, April 30, 2015), the impact location is not visible to Earth. A description of the series of orbital correction maneuvers during March and April 2015 used to raise the spacecraft's altitude, along with illustrations of the position of Earth and Mercury with respect to the Sun at the predicted time of impact, is shown [on the MESSENGER mission website].
MESSENGER will be traveling at 3.9 kilometers per second when it strikes the surface. The twin GRAIL spacecraft were moving at about 1.6 km/s when they hit the Moon in late 2012. The GRAIL impact sites were photographed by the Lunar Reconnaissance Orbiter, revealing craters about 5 meters in diameter. Scaling relationships suggest that the crater made by MESSENGER will be about 16 meters across. MESSENGER image coverage of Mercury at spatial resolutions sufficiently high to recognize 16-meter craters is very limited, therefore it is uncertain whether a future orbital mission that obtains high-resolution images would be able to tell which crater was formed by the MESSENGER impact.

MESSENGER has been in space for more than 10 years now, and in orbit of Mercury since March of 2011. It has sent back over 250,000 images of the planet to us here, giving us an unprecedented look at the innermost planet of our solar system.

This detailed Mercury mosaic was constructed from images sent back by MESSENGER. Credit: NASA

NExSS Coalition Will Search For Life Out In The Universe

It's been around 20 years since scientists discovered the first planet orbiting another star, and estimates now are that every star we can see may have them, but one burning question still remains. Do any of these planets have life?

'Potentially habitable world Kepler-186f.
Credit: NASA

Now, NASA is gathering together a coalition of scientists from different branches to form NExSS - the Nexus for Exoplanet System Science.

According to the NASA Jet Propulsion Laboratory website:

NExSS will tap into the collective expertise from each of the science communities supported by NASA's Science Mission Directorate:
• Earth scientists develop a systems science approach by studying our home planet.
• Planetary scientists apply systems science to a wide variety of worlds within our solar system.
• Heliophysicists add another layer to this systems science approach, looking in detail at how the sun interacts with orbiting planets.
• Astrophysicists provide data on the exoplanets and host stars for the application of this systems science framework.
NExSS will bring together these prominent research communities in an unprecedented collaboration, to share their perspectives, research results, and approaches in the pursuit of one of humanity's deepest questions: Are we alone?

"NExSS scientists will not only apply a systems science approach to existing exoplanet data, their work will provide a foundation for interpreting observations of exoplanets from future exoplanet missions such as [the Transiting Exoplanet Survey Satellite (TESS)], [the James Webb Space Telescope (JWST)], and [the Wide-field Infrared Survey Telescope (WFIRST)]," said Paul Hertz, director of NASA's Astrophysics Division.

Rosetta Captures A Comet Jet In Action

The ESA's Rosetta spacecraft has captured plenty of pictures of Comet 67P/Churyumov-Gerasimenko, very likely enough to keep scientists back here on Earth busy for years sorting out everything they can learn from them.

However, for the first time since the comet began to 'wake up', the spacecraft's OSIRIS camera managed to catch the exact moment when a new jet blasted forth from the comet's surface.

"This was a chance discovery," OSIRIS principal investigator Holger Sierks, from the Max Planck Institute for Solar System Research (MPS), said in a Rosetta blog post. "No one has ever witnessed the wake-up of a dust jet before. It is impossible to plan such an image."

Originating from the Imhotep region of the comet, which OSIRIS scientist Jean-Baptiste Vincent explained was just approaching dawn, it is possible that this jet was caused by sunlight striking the face of one of Imhotep's cliffs.

However, according to the Rosetta blog:

The onset of activity could also be the result of a different type of more explosive activity. That is, the outburst could have been triggered by a wave of heat reaching ices trapped in a deeper layer beneath the surface.
OSIRIS could not continue to observe the new feature after 07:17 CET because Imhotep was soon fully illuminated, making it impossible to discern individual jets in the overexposed coma. It is therefore not clear whether Rosetta witnessed the birth of a continuous jet or a short-lived outburst.

With Rosetta travelling along with Comet 67P through the rest of this year and well into 2016, there will be plenty of time and hopefully plenty more opportunities to see these events before the mission ends.

Sources: NASA | NASA JPL | ESA Rosetta

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