{"id":39428,"date":"2014-12-26T17:10:01","date_gmt":"2014-12-26T09:10:01","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/messenger-and-cassinis-landmark-discoveries-in-2014\/"},"modified":"2014-12-26T17:10:01","modified_gmt":"2014-12-26T09:10:01","slug":"messenger-and-cassinis-landmark-discoveries-in-2014","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/messenger-and-cassinis-landmark-discoveries-in-2014\/","title":{"rendered":"MESSENGER and Cassini\u2019s landmark discoveries in 2014"},"content":{"rendered":"

For NASA, 2014 marked the 10th anniversary of MESSENGER in space and the tenth anniversary of Cassini at Saturn. Throughout the year, the two probes returned valuable scientific data to Earth while scientists revealed the fruits of the probes\u2019 labors through several announcements of groundbreaking discoveries at the two planets, including new information about solar neutrons (Mercury) and the many moons (and one new one) of Saturn.<\/p>\n

MESSENGER:<\/p>\n

Orbiting the closest planet to the Sun, the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft, currently in its second and final mission extension, spent 2014 in its third Earth year of orbital operations at Mercury.<\/p>\n

\"NASASince arriving at Mercury on 18 March 2011, MESSENGER has completed both its primary mission (which ended on 16 March 2012) and its first mission extension (which ended on 17 March 2013).<\/p>\n

Now in its second mission extension, MESSENGER\u2019s scientists have followed-up on and made new discoveries about Mercury and our solar system\u2019s inner-most area.<\/p>\n

In January, scientists writing the Journal of Geophysical Research: Space Physics revealed information gathered from MESSENGER regarding solar wind flows and swirls.<\/p>\n

According the journal article, the solar wind of particles streaming off the sun helps drive flows and swirls in space that are actually just as complicated as terrestrial weather patterns observed on Earth, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune.<\/p>\n

\"2014-12-27Using data collected from MESSENGER, scientists were able to identified for the first time at Mercury a classic space weather event called a Hot Flow Anomaly (HFA), which had previously been spotted at Earth, Venus, Saturn, and Mars.<\/p>\n

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As stated by Vadim Uritsky at NASA\u2019s Goddard Space Flight Center in Greenbelt, Maryland, \u201cPlanets have a bow shock the same way a supersonic jet does. These hot flow anomalies are made of very hot solar wind deflected off the bow shock.\u201d<\/p>\n

In order to find these HFAs at Mercury, the analysis team used MESSENGER to detect the presence of two HFA signatures.<\/p>\n

The first signature led to the detection of magnetic fields that can be used to detect giant electric current sheets that lead to HFAs.<\/p>\n

The second observation looked for the heating signature of the charged particles.<\/p>\n

Scientists were then able analyze this information to quantify the kind of turbulence that existed in the region. This led to the discovery of HFAs at Mercury.<\/p>\n

These observations not only helped prove the existence of HFAs at Mercury, but also helped create a more complete understanding of this type of space weather in general<\/p>\n

In total, HFAs have been observed in a variety of scale sizes \u2013 from around 600 miles across at Venus to closer to 60,000 miles across at Saturn.<\/p>\n

The new study of information gathered by MESSENGER suggests that the most important factor for determining HFA size is the geometry and size of the planet\u2019s bow shock.<\/p>\n

Following from this announcement, scientists reported in July in the Journal of Geophysical Research: Space Physics, that MESSENGER had directly observed solar neutrons.<\/p>\n

\"NASASolar neutrons are created during solar flare events and carry vital information regarding the power of solar flares \u2013 the intense bursts of radiation from the Sun during times of magnetic energy release \u2013 and the processes of solar flares that accelerate solar particles.<\/p>\n

The issue regarding solar neutrons, up until now, is that they have a very short lifespan of approximately 15 minutes and are thus very difficult to detect or observe directly because how far they travel out into space depends on the velocity at which they are ejected from the Sun.<\/p>\n

Based on their lifespan, solar neutrons almost universally die out before reaching near-Earth space (if they\u2019re even ejected in Earth\u2019s direction to begin with).<\/p>\n

To this end, no neutron detectors on Earth or in near-Earth space have ever observed a solar neutron.<\/p>\n

\"2014-12-27However, MESSENGER orbits Mercury at a distance from the Sun of approximately 28 million miles, much closer than the approximate 93 million mile distance between the Earth and the Sun.<\/p>\n

As stated by project scientist David Lawrence at The Johns Hopkins Applied Physics Lab, \u201cTo understand all the processes on the sun, we look at as many different particles coming from the sun as we can \u2013 photons, electrons, protons, neutrons, gamma rays \u2013 to gather different kinds of information.<\/p>\n

\u201cCloser to Earth, we can observe charged particles from the sun, but analyzing them can be a challenge as their journey is affected by magnetic fields.\u201d<\/p>\n

Charged particles tend to twirl and gyrate around the magnetic field lines created by the vast magnetic systems that surround the Sun and the Earth.<\/p>\n

However, neutrons are not electrically charged and travel in straight lines from the flaring region. Therefore, they can carry information about flare processes unperturbed by the environments through which they move.<\/p>\n

\"2014-12-27This is important because solar neutrons can then be used by scientists to decipher one aspect of the complicated acceleration processes that are responsible for the creation of highly energetic and fast solar particles.<\/p>\n

To this end, scientists used data collected by MESSENGER between 4-5 June 2011 of a solar flare accompanied by fast-moving, energetic charged particles to search for any elusive solar neutrons that might have encountered MESSENGER as they passed by.<\/p>\n

This data was then compared to information regarding the solar flare captured by NASA\u2019s solar telescope STEREO (Solar Terrestrial Relations Observatory).<\/p>\n

By combining data from the two spacecraft, scientists were able to determine that MESSENGER detected an increase in the number of solar neutrons at Mercury\u2019s orbit hours before the large number of charged particles (that had been slowed down by their interaction with the Sun\u2019s magnetosphere) associated with the flare reached the spacecraft.<\/p>\n

This indicated that the neutrons were most likely produced by accelerated flare particles striking the lower solar atmosphere, releasing neutrons as a result of high-energy collisions.<\/p>\n

Thus, the MESSENGER and STEREO data together provided new information about how particles are accelerated in solar flares.<\/p>\n

\"2014-12-27As scientists continued to sift through the data being collected by MESSENGER, its operations team turned their attention toward the probe\u2019s 10-year anniversary on 3 August.<\/p>\n

Over the course of the probe\u2019s 10 years in space, MESSENGER travelled 8 billion millions in 29 trips around the sun, returned 255,858 images to Earth, conducted 6 flybys of three of the four inner planets (not Mars), and performed 3,308 orbits of Mercury spanning 7 Mercury solar days and 1,232 Earth days.<\/p>\n

During those orbits of Mercury, MESSENGER conducted 35 million shots of the Mercury Laser Altimeter, returned 10 terabytes of scientific information to Earth that has so far been publically released, and has averaged a speed of 91,730 mph (relative to the Sun).<\/p>\n

Marking the occasion, MESSENGER Mission Operations Manager Andy Calloway, of the Johns Hopkins University Applied Physics Laboratory stated, \u201cWe have operated successfully in orbit for more than three Earth years and more than 14 Mercury years as we celebrate this amazing 10th anniversary milestone.<\/p>\n

\u201cThe MESSENGER spacecraft operates in one of the most challenging and demanding space environments in our Solar System, and we have met that challenge directly through innovation and hard work, as exemplified by the stunning discoveries and data return achievements.<\/p>\n

\u201cOur only regret is that we have insufficient propellant to operate another 10 years, but we look forward to the incredible science returns planned for the final eight months of the mission.\u201d<\/p>\n

And as those final eight months of operations began, MESSENGER\u2019s team continued to advance the mission beyond its original goals.<\/p>\n

\"2014-12-27On 8 October 2014, MESSENGER\u2019s team turned the spacecraft\u2019s camera away from Mercury and toward Earth to observe the 8 October 2014 lunar eclipse.<\/p>\n

At the time of the eclipse, MESSENGER was 107 million km (66 million miles) from Earth, and its viewing angle was nearly perfect as MESSENGER was almost but not quite directly between the Earth and the Sun.<\/p>\n

Thus, from MESSENGER\u2019s viewpoint, the Earth and moon were nearly full.<\/p>\n

The observation was in part a test to see what could be observed as well as part of a growing effort by the scientific community to use still operational but past their original mission timeframes spacecraft to perform non-traditional observations of solar system bodies.<\/p>\n

\"2014-12-27These observations are designed to help planetary scientists understand what various stellar events (that we concretely know about) look like from long distances and how our current technology observes them to help in the detection of such phenomenon in extra-solar planetary systems.<\/p>\n

For example, NASA has used Cassini at Saturn to observe the Transit of Venus (as seen from Saturn) to learn more about and validate extra-solar planetary atmospheric analyses obtained through extra-solar planetary transits.<\/p>\n

In MESSENGER\u2019s case, the observation of the lunar eclipse on 8 October was, in a way, part of a growing desire to detect extra-solar moons either by transit of the moons just before or after the transit of their host planet in front of the host planet\u2019s star or by eclipses of those moons into their host planet\u2019s umbral shadow.<\/p>\n

MESSENGER\u2019s observation of the eclipse was a success, with MESSENGER\u2019s cameras capturing both the Earth and the disappearing moon during the eclipse.<\/p>\n

But for MESSENGER, the end if nearing.<\/p>\n

\"2014-12-27At this time, the probe has enough onboard fuel to perform just one more orbit-raising maneuver \u2013 currently scheduled for 21 January 2015.<\/p>\n

Once this burn is complete, MESSENGER will ostensibly be out of fuel.<\/p>\n

Because the probe is in an orbit with a low periapsis (point in an orbit of closest approach to the center of mass of a stellar body other than the Earth or Sun), these regular orbit-raising maneuvers are needed to keep the spacecraft in a stable orbit.<\/p>\n

Once MESSENGER runs out of fuel, its orbit will slowly decay, and the spacecraft will end its tenure at the innermost planet of our solar system with a crash landing onto the surface of Mercury.<\/p>\n

That crash landing is expected in March 2015.<\/p>\n

Cassini: 10 years exploring the Saturnian system:<\/p>\n

Like MESSENGER, Cassini\u2019s operational team was also looking at 2014 for the commemoration of their craft\u2019s 10 year anniversary at its scientific target: Saturn.<\/p>\n

As Cassini entered 2014 having spent 9.5 years in Saturn orbit, scientists on Earth were busy analyzing data collected by the probe in previous years.<\/p>\n

\"2014-06-30The first 2014 scientific announcement from Cassini data related to a solar event (which created distinct auroras at Saturn\u2019s poles) in April and May 2013 witnessed by both Cassini at Saturn and Hubble from Earth orbit.<\/p>\n

Hubble witnessed the event in ultraviolet wavelength while Cassini garnered close-up views in infrared, visible light, and ultraviolet wavelengths.
\nAs a result of this detailed study, scientists were able to obtain a step-by-step choreography of the auroras\u2019 movements throughout Saturn\u2019s complex magnetic environment.<\/p>\n

Discussing the results of the observation, Jonathan Nichols of the University of Leicester in England, stated that \u201cSaturn\u2019s auroras can be fickle \u2013 you may see fireworks, you may see nothing. In 2013, we were treated to a veritable smorgasbord of dancing auroras, from steadily shining rings to super-fast bursts of light shooting across the pole.\u201d<\/p>\n

\"2014-12-27Images from Cassini\u2019s Ultraviolet Imaging Spectrometer (UVIS) provided scientists with a look at the changing patterns of faint emissions on scales of a few hundred miles and specifically tied the changes in the auroras to the fluctuating wind of charged particles blowing off the sun and flowing past Saturn.<\/p>\n

The data captured by Cassini suggest that one way the bright auroral storms are produced is by the formation of new connections between magnetic field lines in Saturn\u2019s magnetosphere \u2013 the same process that causes auroral storms in the magnetic field around Earth.<\/p>\n

More interestingly for the auroras at Saturn was the discovery that one persistent bright patch of aurora rotated around the planet\u2019s pole in lockstep with the orbital position of Saturn\u2019s moon Mimas.<\/p>\n

Previous observations of auroras at Saturn had shown an intermittently bright spot magnetically linked with the moon Enceladus, but this was the first time that an auroral bright spot was linked with Mimas as well as linked in lockstep rotation for a prolonged amount of time with any one of Saturn\u2019s moons.<\/p>\n

Moreover, these new observations gave scientists unexpected clues to a long-standing mystery about the atmospheres of the giant outer planets.<\/p>\n

\"2014-12-27\u201cScientists have wondered why the high atmospheres of Saturn and other gas giants are heated far beyond what might normally be expected by their distance from the sun,\u201d said Sarah Badman, a Cassini visual and infrared mapping spectrometer team associate at Lancaster University, England.<\/p>\n

\u201cBy looking at these long sequences of images taken by different instruments, we can discover where the aurora heats the atmosphere as the particles dive into it and how long the cooking occurs.\u201d<\/p>\n

With these observations and discoveries in hand, scientists stated in February that they were continuing to evaluate the Hubble and Cassini data of the overall event with the hope of discovering how clouds of charged particles move around Saturn as it spins and receives blasts of solar material from the sun.<\/p>\n

\u201cAs we move into the part of the 11-year solar cycle where the sun is sending out more blobs of plasma, we hope to sort out the differences between the effects of solar activity and the internal dynamics of the Saturn system\u201d, said Marcia Burton, a Cassini fields and particles scientist at NASA\u2019s Jet Propulsion Laboratory.<\/p>\n

As these results from 2013 data were released, Cassini\u2019s operational team continued to gather scientific data that scientists would use to unlock the secrets of the second largest planet in our solar system and its complex system of moons.<\/p>\n

\"2014-12-27Specifically, of the two moons of primary scientific interest for Cassini and its team, the 100th flyby of Titan was quickly approaching.<\/p>\n

On 6 March 2014, the Cassini spacecraft dived to within 933 miles (15,000 km) of Titan to perform the landmark 100th flyby of the Saturn moon.<\/p>\n

In the previous 99 flybys of Titan, Cassini had helped unlock many of the mysteries surrounding this moon, which a decade earlier was just a fuzzy orange ball about the size of Mercury with a nitrogen atmosphere.<\/p>\n

With these first 99 flybys, knowledge of Titan increased dramatically with the categorization of most of the moon\u2019s surface features, including its liquid methane and ethane lakes, and the categorization of the seasonal terrain changes on the moon as seasonal floods of liquid methane and ethane carve new patterns into Titan\u2019s surface.<\/p>\n

\"2014-06-30Following this 100th flyby of Titan, Cassini and its teams re-oriented the spacecraft for continual observation of Saturn while setting up for another flyby of Titan in June.<\/p>\n

As Cassini continued observations, scientists announced in April that years of collective data from the Cassini orbiter had concretely found evidence for a large underground ocean of liquid water on Saturn\u2019s moon Enceladus \u2013 the second of the two moons of primary scientific interest for Cassini.<\/p>\n

A large subterranean saltwater ocean on Enceladus had long been suspected from data returned by Cassini through close flybys of the moon in previous years.<\/p>\n

Previous flybys of Enceladus between 2009 and 2012 provided stronger evidence that the moon harbors a large, salt-water ocean beneath its surface.<\/p>\n

This strong evidence was finally confirmed by NASA in April 2014.<\/p>\n

This significant discovery, along with the confirmation (through analysis of the ejecta material from the cryo-geysers) that the ocean harbors organic molecules and nutrients and has a permanent heat source (caused by gravitational heating by Saturn as Enceladus orbits the massive planet and is therefore squeezed and elongated) threw Enceladus to the near top of the list of \u201cbest places in the solar system to host alien microbial life.\u201d<\/p>\n

Following very close to this confirmation, NASA scientists also revealed that Cassini had captured the birth of a new moon in one of Saturn\u2019s rings.<\/p>\n

\"2014-12-27Based on images captured on 15 April 2013, NASA scientists revealed on 14 April 2014 that disturbances seen by Cassini at the very edge of Saturn\u2019s A-ring \u2013 the outermost of the planet\u2019s large rings \u2013 was in fact the formation of a small icy object that may be a new moon.<\/p>\n

The object in question is 20 percent brighter than the surrounding material, is 750 miles (1,200 km) long and 6 miles (10 km) wide, and was found by the detection of unusual protuberances in the usually smooth profile of the A-ring\u2019s edge.<\/p>\n

\u201cWe have not seen anything like this before,\u201d said Carl Murray of Queen Mary University of London, lead author of the report that identified the possible moon. \u201cWe may be looking at the act of birth, where this object is just leaving the rings and heading off to be a moon in its own right.\u201d<\/p>\n

Continuing the series of revelations about Saturn\u2019s moon came the announcement that scientists, working with data from Cassini, had developed a new way to understand the atmospheres of exoplanets by using Titan as a stand-in.<\/p>\n

\"2014-12-27This new understanding demonstrates the significant impact of hazy skies on our ability to learn about the worlds orbiting distant stars.<\/p>\n

Currently, scientists are able to discern characteristics of an exoplanet by collecting the light that passes through that exoplanet\u2019s atmosphere as it transits in front of its host star.<\/p>\n

As that transit occurs, some of the star\u2019s light travels through the exoplanet\u2019s atmosphere where it is changed in subtle, but measurable, ways. As this happens, the exoplanet\u2019s atmospheric and terrestrial (if it is a terrestrial planet) characteristics are imprinted onto that light.<\/p>\n

The light is then captured by telescopes and broken down into its spectra \u2013 where the recorded imprint is then studied.<\/p>\n

\"2014-12-27One particular problem with this method of teasing out an exoplanet\u2019s characteristics is that overly hazy atmospheres can distort some of the data that get imprinted onto the light spectra.<\/p>\n

But the significance of the data distortion was not well known.<\/p>\n

To accurately determine how overly hazy atmospheres distort that data, scientists turned to Cassini\u2019s observations of Titan.<\/p>\n

Specifically, the scientific team exploited a similarity between exoplanet transits and sunsets witnessed by the Cassini spacecraft at Titan. These observations by Cassini, called solar occultations (in this case, when Titan passed directly between Cassini and its line-of-sight to the Sun), effectively allowed scientists to observe Titan as if it was a transiting exoplanet.<\/p>\n

As the alignment between Cassini, Titan, and the Sun took Titan across the disc of the Sun, Cassini collected the light data that streamed through Titan\u2019s atmosphere. Scientists then took that data (which, at the time of observation between 2006 and 2011 was not actually being collected for this particular work) and broke the light down into its spectra.<\/p>\n

\"2014-12-27Scientists then examined the characteristics of the light spectra and ran an analysis of Titan\u2019s characteristics as if it was a completely unknown exoplanet. They then compared that data to the definitive characteristics of Titan that have been directly observed.<\/p>\n

In the process, Titan\u2019s sunsets revealed just how dramatic the effects of hazes can be.<\/p>\n

In all, it was found that hazes high above some transiting exoplanets might strictly limit what their spectra can reveal to planet transit observers. Basically, the observations might only be able to gather information from a planet\u2019s upper atmosphere.<\/p>\n

On Titan, that corresponds to about 90 to 190 miles (150 to 300 kilometers) above the moon\u2019s surface, high above the bulk of its dense and complex atmosphere.<\/p>\n

Moreover, hazes more strongly affect shorter wavelengths, or bluer, colors of light. Studies of exoplanet spectra have commonly assumed that hazes would affect all colors of light in similar ways.<\/p>\n

Studying sunsets through Titan\u2019s hazes has revealed that this is not the case.<\/p>\n

See Also<\/h4>\n