Missions Archives

April 6, 2013December 23, 2015 by Ken Kremer

Terran Fleet at Mars Takes a Break for Conjunction – Enjoy the Video and Parting View

Curiosity and Mount Sharp - Parting Shot ahead of Solar Conjunction. Enjoy this parting view of Curiosity's elevated robotic arm and drill are staring at you - back dropped with her ultimate destination - Mount Sharp - in this panoramic vista of Yellowknife Bay basin snapped on March 23, Sol 223, by the rover's navigation camera system. The raw images were stitched by Marco Di Lorenzo and Ken Kremer and colorized. Credit: NASA/JPL-Caltech/Marco Di Lorenzo/KenKremer (kenkremer.com). See video below explaining Mars Solar Conjunction

Curiosity and Mount Sharp – Parting Shot ahead of Mars Solar Conjunction
Enjoy this parting view of Curiosity’s elevated robotic arm and drill staring at you; back dropped with her ultimate destination – Mount Sharp – in this panoramic vista of Yellowknife Bay basin snapped on March 23, Sol 223, by the rover’s navigation camera system. The raw images were stitched by Marco Di Lorenzo and Ken Kremer and colorized. Credit: NASA/JPL-Caltech/Marco Di Lorenzo/KenKremer (kenkremer.com)
See video below explaining Mars Solar Conjunction[/caption]

Earth’s science invasion fleet at Mars is taking a break from speaking with their handlers back on Earth.

Why ? Because as happens every 26 months, the sun has gotten directly in the way of Mars and Earth.

Earth, Mars and the Sun are lined up in nearly a straight line. The geometry is normal and it’s called ‘Mars Solar Conjunction’.

Conjunction officially started on April 4 and lasts until around May 1.

From our perspective here on Earth, Mars will be passing behind the Sun.

Watch this brief NASA JPL video for an explanation of Mars Solar Conjunction.

Therefore the Terran fleet will be on its own for the next month since the sun will be blocking nearly all communications.

In fact since the sun can disrupt and garble communications, mission controllers will be pretty much suspending transmissions and commands so as not to inadvertently create serious problems that could damage the fleet in a worst case scenario.

Right now there are a trio of orbiters and a duo of rovers from NASA and ESA exploring Mars.

The spacecraft include the Curiosity (MSL) and Opportunity (MER) rovers from NASA. Also the Mars Express orbiter from ESA and the Mars Odyssey (MO) and Mars Reconnaissance Orbiter (MRO) from NASA.

Because several of these robotic assets have been at Mars for nearly 10 years and longer, the engineering teams have a lot of experience with handling them during the month long conjunction period.

“This is our sixth conjunction for Odyssey,” said Chris Potts of JPL, mission manager for NASA’s Mars Odyssey, which has been orbiting Mars since 2001. “We have plenty of useful experience dealing with them, though each conjunction is a little different.”

But there is something new this go round.

“The biggest difference for this 2013 conjunction is having Curiosity on Mars,” Potts said. Odyssey and the Mars Reconnaissance Orbiter relay almost all data coming from Curiosity and the Mars Exploration Rover Opportunity, as well as conducting the orbiters’ own science observations.

The rovers and orbiters can continue working and collecting science images and spectral data.

But that data will all be stored in the on board memory for a post-conjunction playback starting sometime in May.

Ken Kremer

…………….

Learn more about Curiosity’s groundbreaking discoveries and NASA missions at Ken’s upcoming lecture presentations:

April 20/21 : “Curiosity and the Search for Life on Mars – (in 3-D)”. Plus Orion, SpaceX, Antares, the Space Shuttle and more! NEAF Astronomy Forum, Suffern, NY

April 28: “Curiosity and the Search for Life on Mars – (in 3-D)”. Plus the Space Shuttle, SpaceX, Antares, Orion and more. Washington Crossing State Park, Titusville, NJ, 130 PM

April 4, 2013December 23, 2015 by Nancy Atkinson

Solar Spacecraft Gets a Little Loopy

Our own Sun produces flares, but we are protected by our magnetosphere, and by the distance from the Sun to Earth. Credit: NASA/ Solar Dynamics Observatory,

Twice a year, the Solar Dynamics Observatory performs a 360-degree roll about the axis on which it points toward the Sun. This produces some unique views, but the rolls are necessary to help calibrate the instruments, particularly the Helioseismic and Magnetic Imager (HMI) instrument, which is making precise measurements of the solar limb to study the shape of the Sun. The rolls also help the science teams to know how accurately the images are aligned with solar north.

But take this rolling imagery, add some goofy music and hopefully it adds a smile to your day!

April 2, 2013December 23, 2015 by Jason Major

NASA Trailer Achieves Crowdfunding Goal to Run Before Star Trek: Into Darkness

Here’s one bit of NASA outreach that won’t be affected by suspensions or sequesters: an edited version of “We Are The Explorers,” a video highlighting the past successes and future goals of the space administration — created by NASA and featuring an inspiring narration by Peter “Optimus Prime” Cullen — will be screened in several major U.S. cities during the premiere of Star Trek Into Darkness thanks to an overwhelmingly successful crowdfunding effort on Indiegogo.com.

Now that the initial goal of $33,000 has been met and the 30-second ad spot can be purchased, the team responsible for the campaign (Aerospace Industries Association of America) will use any funds donated during the next 29 days to reach its next target: getting the ad in at least one theater in every state in America for two weeks. In order for that to happen, a grand total of $94,000 will need to be reached.

Want to help make it so? Find out more about how you can contribute:

According to the Indiegogo campaign page, “If we raise our funding total to $94,000, students, young people, and the general public will see this video from coast to coast. This new goal will expand our reach from 59 movie theater screens to 750 screens!”

That means a lot more chances that the spot will run at the theater where you go to see the new Star Trek film when it comes out on May 17. (Because you know you’re going to go see it, let’s be honest. It’s Star Trek.)

And because it’s Indiegogo you’ll get a “perk” depending on the amount you contribute, ranging from digital copies of the final spot to DVD copies of the excellent HBO series “From Earth to the Moon” (while supplies last.) Because the initial goal has been met, some perks are already sold out… but then, contributing to something as important as space exploration isn’t about the stuff you get, it’s about the message you can give.

“This is more than a fundraiser, it’s a demonstration of support for space exploration programs. By donating to this campaign, you’re making a very powerful statement about the widespread enthusiam that exists for space programs. A crowdfunding campaign is the best vehicle to deliver this message. By reaching our goal, we not only enable a first-of-its-kind ad campaign, we also demonstrate that countless people support a strong space program that’s in development.”

You can contribute here, and be sure to spread the word too. That way, when you’re looking at the video on the big screen, when you see them putting Al Shepard’s gloves on, when you see the fiery exhaust of the Saturn rocket and you hear Cullen’s voice rumble “we are the explorers,” you can know that you helped make it happen — and that somewhere in that same theater a young mind may very well be inspired to continue the exploration.

Maybe that mind might even be be your own.

“Our next destination awaits. We don’t know what new discoveries lie ahead, but this is the very reason we must go.“

This crowdfunding campaign is the work of the Aerospace Industries Association (AIA) of America. This campaign is not endorsed by NASA nor is it conducted at their direction or request. Note: by donating you acknowledge that donations are not tax deductible.

April 2, 2013December 23, 2015 by Nancy Atkinson

MAVEN’s Magnetometer Will Look Back in Time

Artist depiction of the MAVEN spacecraft. Credit: NASA

The next mission to the Red Planet, the Mars Atmosphere and Volatile Evolution (MAVEN) will be the first spacecraft ever to make direct measurements of the Martian atmosphere. MAVEN will carry eight science instruments, including a magnetometer that will investigate what remains of Mars’ magnetic “shield,” and will, in essence, help to look back in time at what may have happened to a planet once thought to have an abundance of liquid water but is now a frozen desert. The magnetometer will play a key role in studying the planet’s atmosphere and interactions with solar wind, helping answer the question of why Mars lost much of its atmosphere.

“The magnetometer helps us see where the atmosphere is protected by mini-magnetospheres and where it’s open to solar wind,” said Jack Connerney, a co-investigator for the mission. “We can study the solar wind impact and how efficient it is at stripping the atmosphere.”

By measuring sections of the planet’s magnetic field, the magnetometer could help scientists create a bigger picture of the planet’s overall atmosphere.

MAVEN is the first mission to Mars specifically designed to help scientists understand the past – and also the ongoing — escape of CO2 and other gases into space. MAVEN will orbit Mars for at least one Earth-year, about a half of a Martian year. MAVEN will provide information on how and how fast atmospheric gases are being lost to space today, and infer from those detailed studies what happened in the past.

Studying how the Martian atmosphere was lost to space can reveal clues about the impact that change had on the Martian climate, geologic, and geochemical conditions over time, all of which are important in understanding whether Mars had an environment able to support life.

MAVEN is scheduled to launch in 2013, with a launch window from Nov. 18 to Dec 7, 2013. Mars Orbit Insertion will be in mid-September2014.

Find out more about MAVEN at the mission website.

March 22, 2013December 23, 2015 by Jason Major

MESSENGER Sees a Smoother Side of Mercury

A high-resolution view of a "silky" surface on Mercury

During its two years in orbit around Mercury — as well as several more years performing flybys — the MESSENGER spacecraft has taken over 150,000 images of the innermost planet, giving us a look at its incredibly rugged, Sun-scoured surface like never before. But not all areas on Mercury appear so harsh — it has its softer sides too, as seen above in an image released earlier today.

Here we see the smooth walls, floor and upper surfaces around an irregular depression on Mercury in high definition. The velvety texture is the result of widespread layering of fine particles, because unlike many features on Mercury’s ancient surface this rimless depression wasn’t caused by an impact from above but rather explosively escaping lava from below — this is the rim of a volcanic vent, not a crater!

Previous images have been acquired of this irregularly-shaped depression but this is the highest resolution view MESSENGER has captured to date — about 26 meters per pixel.

A wide-angle view of the same depression, captured in July 2012 — A wide-angle view of the same depression, captured by MESSENGER in July 2012

The full depression, located northeast of the Rachmaninoff basin, is about 36 km (22 miles) across at its widest. It’s surrounded by a smooth blanket of high-reflectance material — explosively ejected volcanic particles from a pyroclastic eruption that spread over the surface like snow.

Other similar vents have been found on Mercury, like this heart-shaped one in Caloris basin. The smooth, bright surface material is a telltale sign of a volcanic outburst, as are the rimless, irregular shapes of the vents.

The numerous small craters that are seen inside the vent and on the smooth surrounding surfaces would be from meteorite impacts that occurred well after the eruption.

On March 17, 2011, MESSENGER became the first spacecraft ever to orbit the planet Mercury. It is capable of continuing orbital operations until early 2015. Find out more about the mission here.

Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

March 20, 2013April 26, 2016 by David Dickinson

U.S. To Restart Plutonium Production for Deep Space Exploration

A marshmellow-sized Pu-238 pellet awaits a space mission. (Credit: The Department of Energy).

The end of NASA’s plutonium shortage may be in sight. On Monday March 18^th, NASA’s planetary science division head Jim Green announced that production of Plutonium-238 (Pu-238) by the United States Department of Energy (DOE) is currently in the test phases leading up to a restart of full scale production.

“By the end of the calendar year, we’ll have a complete plan from the Department of Energy on how they’ll be able to satisfy our requirement of 1.5 to 2 kilograms a year.” Green said at the 44^th Lunar and Planetary Science Conference being held in Woodlands, Texas this past Monday.

This news comes none too soon. We’ve written previously on the impending Plutonium shortage and the consequences it has for future deep space exploration. Solar power is adequate in most cases when you explore the inner solar system, but when you venture out beyond the asteroid belt, you need nuclear power to do it.

Production of the isotope Pu-238 was a fortunate consequence of the Cold War. First produced by Glen Seaborg in 1940, the weapons grade isotope of plutonium (-239) is produced via bombarding neptunium (which itself is a decay product of uranium-238) with neutrons. Use the same target isotope of Neptunium-237 in a fast reactor, and Pu-238 is the result. Pu-238 produces 280x times the decay heat at 560 watts per kilogram versus weapons grade Pu-239 and is ideal as a compact source of energy for deep space exploration.

Since 1961, over 26 U.S. spacecraft have been launched carrying Multi-Mission Radioisotope Thermoelectric Generators (MMRTG, or formerly simply RTGs) as power sources and have explored every planet except Mercury. RTGs were used by the Apollo Lunar Surface Experiments Package (ALSEP) science payloads left on by the astronauts on the Moon, and Cassini, Mars Curiosity and New Horizons enroute to explore Pluto in July 2015 are all nuclear powered.

Plutonium powered RTGs are the only technology that we have currently in use that can carry out deep space exploration. NASA’s Juno spacecraft will be the first to reach Jupiter in 2016 without the use of a nuclear-powered RTG, but it will need to employ 3 enormous 2.7 x 8.9 metre solar panels to do it.

The plutonium power source inside the Mars Science Laboratory's MMRTG during assembly at the Idaho National Laboratory. (Credit: Department of Energy?National Laboratory image under a Creative Commons Generic Attribution 2.0 License). — The plutonium power source inside the Mars Science Laboratory’s MMRTG during assembly at the Idaho National Laboratory. (Credit: Department of Energy/Idaho National Laboratory image under a Creative Commons Generic Attribution 2.0 License).

The problem is, plutonium production in the U.S. ceased in 1988 with the end of the Cold War. How much Plutonium-238 NASA and the DOE has stockpiled is classified, but it has been speculated that it has at most enough for one more large Flag Ship class mission and perhaps a small Scout class mission. Plus, once weapons grade plutonium-239 is manufactured, there’s no re-processing it the desired Pu-238 isotope. The plutonium that currently powers Curiosity across the surface of Mars was bought from the Russians, and that source ended in 2010. New Horizons is equipped with a spare MMRTG that was built for Cassini, which was launched in 1999.

Technicians handle an RTG at the Payload Hazardous Servicing Facility at the Kennedy Space Center for the Cassini spacecraft. (Credit: NASA).

As an added bonus, plutonium powered missions often exceed expectations as well. For example, the Voyager 1 & 2 spacecraft had an original mission duration of five years and are now expected to continue well into their fifth decade of operation. Mars Curiosity doesn’t suffer from the issues of “dusty solar panels” that plagued Spirit and Opportunity and can operate through the long Martian winter. Incidentally, while the Spirit and Opportunity rovers were not nuclear powered, they did employ tiny pellets of plutonium oxide in their joints to stay warm, as well as radioactive curium to provide neutron sources in their spectrometers. It’s even quite possible that any alien intelligence stumbles upon the five spacecraft escaping our solar system (Pioneer 10 & 11, Voyagers 1 & 2, and New Horizons) could conceivably date their departure from Earth by measuring the decay of their plutonium power source. (Pu-238 has a half life of 87.7 years and eventually decays after transitioning through a long series of daughter isotopes into lead-206).

New Horizons in the Payload Hazardous Servicing Facility at the Kennedy Space Center. Note the RTG (black) protruding from the spacecraft. (Credit: NASA/Uwe W.)

The current production run of Pu-238 will be carried out at the Oak Ridge National Laboratory (ORNL) using its High Flux Isotope Reactor (HFIR). “Old” Pu-238 can also be revived by adding newly manufactured Pu-238 to it.

“For every 1 kilogram, we really revive two kilograms of the older plutonium by mixing it… it’s a critical part of our process to be able to utilize our existing supply at the energy density we want it,” Green told a recent Mars exploration planning committee.

Still, full target production of 1.5 kilograms per year may be some time off. For context, the Mars rover Curiosity utilizes 4.8 kilograms of Pu-238, and New Horizons contains 11 kilograms. No missions to the outer planets have left Earth since the launch of Curiosity in November 2011, and the next mission likely to sport an RTG is the proposed Mars 2020 rover. Ideas on the drawing board such as a Titan lake lander and a Jupiter Icy Moons mission would all be nuclear powered.

Engineers perform a fit check of the MMRTG on Curiousity at the Kennedy Space Center. The final installation of the MMRTG occured the evening prior to launch. (Credit: NASA/Cory Huston). — Engineers perform a fit check of the MMRTG on Curiosity at the Kennedy Space Center. The final installation of the MMRTG occurred the evening prior to launch. (Credit: NASA/Cory Huston).

Along with new plutonium production, NASA plans to have two new RTGs dubbed Advanced Stirling Radioisotope Generators (ASRGs) available by 2016. While more efficient, the ASRG may not always be the device of choice. For example, Curiosity uses its MMRTG waste heat to keep instruments warm via Freon circulation. Curiosity also had to vent waste heat produced by the 110-watt generator while cooped up in its aero shell enroute to Mars.

Cutaway diagram of the Advanced Stirling Radioisotope Generator. (Credit: DOE/NASA).

And of course, there are the added precautions that come with launching a nuclear payload. The President of the United States had to sign off on the launch of Curiosity from the Florida Space Coast. The launch of Cassini, New Horizons, and Curiosity all drew a scattering of protesters, as does anything nuclear related. Never mind that coal fired power plants produce radioactive polonium, radon and thorium as an undesired by-product daily.

An RTG (in the foreground on the pallet) left on the Moon by astronauts during Apollo 14. (Credit: NASA/Alan Shepard).

Said launches aren’t without hazards, albeit with risks that can be mitigated and managed. One of the most notorious space-related nuclear accidents occurred early in the U.S. space program with the loss of an RTG-equipped Transit-5BN-3 satellite off of the coast of Madagascar shortly after launch in 1964. And when Apollo 13 had to abort and return to Earth, the astronauts were directed to ditch the Aquarius Landing Module along with its nuclear-powered science experiments meant for the surface of the Moon in the Pacific Ocean near the island of Fiji. (They don’t tell you that in the movie) One wonders if it would be cost effective to “resurrect” this RTG from the ocean floor for a future space mission. On previous nuclear-equipped launches such as New Horizons, NASA placed the chance of a “launch accident that could release plutonium” at 350-to-1 against Even then, the shielded RTG is “over-engineered” to survive an explosion and impact with the water.

But the risks are worth the gain in terms of new solar system discoveries. In a brave new future of space exploration, the restart of plutonium production for peaceful purposes gives us hope. To paraphrase Carl Sagan, space travel is one of the best uses of nuclear fission that we can think of!

March 19, 2013December 23, 2015 by Nancy Atkinson

Remains of GRAIL Spacecraft Found on Lunar Surface

Before and after the GRAIL twins impacts on the Moon December 17, 2012. The LROC Narrow Angle Camera (NAC) directors were able to resolve the impact sites on February 28, 2013, revealing both to be about 5 meters in diameter. Upper panels show the area before the impact; lower panels after the impact. Arrows point to crater locations. LROC NAC observations M186085512R, M186078336L, M1116736474R and M1116736474L. Credit: NASA/GSFC/Arizona State University.

On December 17, 2012, the GRAIL mission came to an end, and the two washing machine-sized spacecraft performed a flying finale with a planned formation-flying double impact into the southern face of 2.5-kilometer- (1.5-mile-) tall mountain on a crater rim near the Moon’s north pole. The Lunar Reconnaissance Orbiter has now imaged the impact sites, which show evidence of the crashes.

But surprisingly, these impacts were not what was expected, says the LRO and GRAIL teams. The ejecta around both craters is dark. Usually, ejecta from craters is lighter in color – with a higher reflectance – than the regolith on surface.

“I expected the ejecta to be bright,” said LROC PI Mark Robinson at a press conference from the Lunar and Planetary Science Conference today, “because everybody knows impact rays on the Moon are bright. We are speculating it could be from hydrocarbons from the spacecraft.”

GRAIL A site seen before and after the impact event. Crater center is located at 75.609°N, 333.407°E/ Credit: NASA/GSFC/Arizona State University.

Typically ejecta from craters is brighter, since subsurface regolith tends to have a higher reflectance. The lunar regolith on the surface tends to be darker because of its exposure to the vacuum of space, cosmic radiation, solar wind bombardment, and micrometeorite impacts. Slowly over time, these processes tend to darken the surface soil.

Robinson said the hydrocarbons could have come from fuel left in the fuel lines (JPL estimated a quarter to half a kilogram of fuel may have remained in the spacecraft – so, not very much) or from the spacecraft itself, which is made out of carbon material.

GRAIL B site seen before and after impact event. Crater center is located at 75.651°N, 333.168°E. Credit: NASA/GSFC/Arizona State University.

Additionally, the impact craters’ shapes were not as expected. The impacts formed craters about 5 m (15 ft) in diameter, and there is little ejecta to the south – the direction from which the spacecraft were traveling. “The spacecraft came in at a 1 or 2 degree impact angle,” said Robinson, “so this not a normal impact, as all the ejecta went upstream in the direction of travel.”

“I was expecting to see skid marks, myself,” said GRAIL principal investigator Maria Zuber. She added that she was committed to using every bit of fuel to mapping the gravity field at as low an altitude as possible. “I was determined that we would not end the mission with unused fuel because that would have meant we could mapped it even lower.

The spacecraft did end up being able to map the Moon from 2 km above the surface, the lowest altitude from which any planetary surface has ever been mapped, creating an extremely high resolution map.

LRO Wide Angle Camera (WAC) image of the GRAIL impact area on the south side of the unnamed massif. Credit: NASA/GSFC/ASU.

Robinson said he was skeptical that they could find the impact craters, since the team has yet to find the impact sites of the Apollo ascent stages, which should be much bigger than the GRAIL impacts.

“Finding the impact crater was like finding a needle in haystack,” Robinson said, “as the images are looking at an area that is about 8 km wide and 30 to 40 km tall, and we were looking for something that is a couple of pixels wide.”

Robinson said he spent hours looking for it with no luck, only to see it later when he was on a conference call and was just looking at it out of the corner of his eye.

“It was really fun to find the craters,” he said. LRO did take images in early January, but better images were taken on February 28, 2013.

While LRO’s camera was not able to image the actual impact since it occurred on the night-side of the Moon, the LAMP instrument (Lyman Alpha Mapping Project) on LRO was able to detect the plumes of the impacts.

Kurt Retherford, PI of LAMP said the UV spectrograph was pointed towards the limb of the Moon — and actually looking in the direction of the constellation Orion at the time of the GRAIL impact — to observe the gases coming out of the plumes. They did detect the two impact plumes which clearly showed an excess of emissions from hydrogen atoms. “We were excited to see this detection of atomic hydrogen coming from the impact sites,” Retherford said. “This is our first detection of native hydrogen atoms from the lunar environment.”

This video shows LRO as it flies over the north pole of the Moon, where it has a very good view of the GRAIL impact. The second part is the view from LRO through LAMP’s slit, showing the impact and the resulting plume. The orbits, impact locations, terrain, LAMP field of view, and starfield are accurately rendered.

Retherford said further studies from this will help in determining the processes of how the implantation of solar wind protons on the lunar surface could create the water and hydroxyl that has been recently detected on the lunar surface by other spacecraft and in studies of lunar rocks returned by the Apollo missions.

You can see more images from LRO on the LROC website. Additionally, NASA has now issued a press release about this, too.

March 18, 2013December 23, 2015 by Elizabeth Howell

5 Mercury Secrets Revealed by MESSENGER

Artist's concept of MESSENGER in orbit around Mercury. Courtesy of NASA

After two years of doing the loop-the-loop around Mercury, MESSENGER has unveiled a bunch of surprises from Mercury — the closest planet to the Sun.

The spacecraft launched in 2004 and made three flybys of the planet before settling into orbit two years ago today. Incredibly, MESSENGER is only the second NASA probe to visit Mercury; the first one, Mariner 10, only flew by a few times in the 1970s. It was an incredible feat for the time, but we didn’t even have a complete map of Mercury before MESSENGER arrived at the planet.

So, what have scientists found in MESSENGER’s two years in orbit? Tales of sulfur, organic materials and iron, it turns out.

Mercury’s south pole has a weak spot

Magnetic field lines differ at Mercury's north and south poles As a result of the north-south asymmetry in Mercury's internal magnetic field, the geometry of magnetic field lines is different in Mercury's north and south polar regions. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington — Magnetic field lines differ at Mercury’s north and south poles As a result of the north-south asymmetry in Mercury’s internal magnetic field, the geometry of magnetic field lines is different in Mercury’s north and south polar regions. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The magnetic field lines converge differently at the north and south poles of Mercury. What does this mean? There’s a larger “hole” at the south pole for charged particles to do their thing to the surface of Mercury. At the time this information was released, NASA said it’s possible that space weathering or erosion would be different at the north and south poles because of this. Charged particles on the surface would also add to Mercury’s wispy atmosphere.

How the atmosphere changes according to distance from the sun

Comparison of neutral sodium observed during MESSENGER’s second and third Mercury flybys. Credit: NASA

Wondering about the atmosphere on Mercury? It depends on the season, and also the element. The scientists found striking changes in calcium, magnesium and sodium when the planet was closer to and further from the sun.

“A striking illustration of what we call ‘seasonal’ effects in Mercury’s exosphere is that the neutral sodium tail, so prominent in the first two flybys, is 10 to 20 times less intense in emission and significantly reduced in extent,” said participating scientist Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory in 2009. “This difference is related to expected variations in solar radiation pressure as Mercury moves in its orbit and demonstrates why Mercury’s exosphere is one of the most dynamic in the solar system.”

Discovery of water ice and organics

A radar image of Mercury’s north polar region is shown superposed on a mosaic of MESSENGER images of the same area. All of the larger polar deposits are located on the floors or walls of impact craters. Deposits farther from the pole are seen to be concentrated on the north-facing sides of craters. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory

Late in 2012, NASA finally was able to corroborate some science results from about 20 years ago. Scientists on Earth saw “radar bright” images from Mercury in the 1990s, implying that there was ice and organic materials at the poles. MESSENGER finally confirmed that through three separate lines of investigation that were published in Science in 2012. Scientists estimated the planet holds between 100 billion and 1 trillion tons of water ice, perhaps as deep as 20 meters in some places. “Water ice passed three challenging tests and we know of no other compound that matches the characteristics we have measured with the MESSENGER spacecraft,” said MESSENGER principal investigator Sean Solomon in a NASA briefing.

Mercury has a big iron core

The internal structure of Mercury is very different from that of the Earth. The core is a much larger part of the whole planet in Mercury and it also has a solid iron-sulfur cover. As a result, the mantle and crust on Mercury are much thinner than on the Earth. Credit: Case Western Reserve University — The internal structure of Mercury is very different from that of the Earth. The core is a much larger part of the whole planet in Mercury and it also has a solid iron-sulfur cover. As a result, the mantle and crust on Mercury are much thinner than on the Earth.
Credit: Case Western Reserve University

While scientists knew before that Mercury has an iron core, the sheer size of it surprised scientists. At 85%, the proportion of the core to the rest of the planet dwarfs its rocky solar system companions. Further, scientists measured Mercury’s gravity. From that, they were surprised to see that the planet had a partially liquid core. “The planet is sufficiently small that at one time many scientists thought the interior should have cooled to the point that the core would be solid,” stated Case Western Reserve University’s Steven A. Hauck II, a co-author of a paper on the topic that appeared in Science Express.

The surface is sulfur-rich

A global view of Mercury, as seen by MESSENGER. Credit: NASA

At some point in Mercury’s history, it’s possible that it could have had lavas erupt and sprinkle the surface with sulfur, magnesium and similar materials. At any rate, what is known for sure is there is quite a bit of sulfur on Mercury’s surface. “None of the other terrestrial planets have such high levels of sulfur. We are seeing about ten times the amount of sulfur than on Earth and Mars,” said paper author Shoshana Weider of the Carnegie Institution of Washington.

March 13, 2013December 23, 2015 by Elizabeth Howell

How the Space Shuttle Killed an American Halley’s Comet Mission

Halley's Comet, as seen by the European Giotto probe. Credit: Halley Multicolor Camera Team, Giotto Project, ESA

NASA missed the chance to visit Halley’s Comet in 1986 when the famed sentinel swung close to Earth, as it does every 76 years. Luckily for history, the Europeans flew Giotto past it on this day (March 13) in 1986, and some other nations sent their own probes.

The full story of NASA’s withdrawal is in Bruce Murray’s Journey Into Space: The First Three Decades of Space Exploration. Murray, the former director of the Jet Propulsion Laboratory, has chapters upon chapters on Halley, but here are some notable highlights.

First of all, there were at least three initiatives for NASA to send a mission to the famed comet. The missions below are in chronological order, and it appears it was only when the preceding one was killed that the next was envisioned:

– Solar sail. This mission would use the power of the solar wind — bits streaming from the sun — to bring a spacecraft within Halley’s gravitational influence. In fact, the spacecraft would stay with Halley as it whisked out of the solar system and would return (long dead) when Halley came back in 2061.

– A rendezvous with Comet Tempel 2. Another idea would see a spacecraft swing close to Comet Tempel 2 but also have a probe that would take a picture of Halley from a distance. NASA also considered splitting the mission in two to meet annual budgetary requirements, but the Comet Science Working Group was cool to the idea. There also was some thought about bringing the Europeans into this mission, but that never worked out.

– Galileo-type hardware. A third initiative had the Jet Propulsion Laboratory envisioning a distant flyby of Halley, basically using similar types of parts that flew in a spacecraft (called Galileo) to Jupiter.

All three of these initiatives fell to budget cuts during the 1970s and 1980s. What caused the budget cuts? In large part, the space shuttle program. To be sure, the shuttle was an impressive piece of hardware, and we are not doubting what it contributed to the construction of the International Space Station and to human spaceflight in general. But it was a large project and in those tight times, something had to give.

Perhaps the most interesting cancellation came in 1979, when NASA administrator Robert Frosch and his deputy went to President Jimmy Carter’s office to plead for the case of two projects: a solar electric propulsion system that would eventually power the Halley-Tempel 2 mission, and the Compton Gamma Ray Observatory (which flew into space, after many delays, in 1991).

Carter, according to Murray, was reading a book on black holes penned by Walter Sullivan of the New York Times. (We’re assuming it’s the 1979 book Black Holes: The Edge of Space, the End of Time.) When presented with the options, Carter said he was “partial to the gamma-ray thing because of this connection with the black-hole problem.”

That signaled the beginning of the end for NASA’s Halley-Tempel 2 mission.

March 13, 2013April 26, 2016 by David Dickinson

WISE Nabs the Closest Brown Dwarfs Yet Discovered

WISE J104915.57-531906 from NASA's WISE survey (centered) and resolved to should its binary nature by the Gemini Observatory (inset). (Credit: NASA/JPL/Gemini Observatory/AURA/NSF).

We now know our stellar neighbors just a little better, and a new discovery may help tell us how common brown dwarfs are in our region of the galaxy. Early this week, researchers at Pennsylvania State University announced the discovery of a binary brown dwarf system. With a parallax measurement of just under 0.5”, this pair is only 6.5 light years distant making it the third closest system to our own and the closest example of the sub-stellar class of objects known as brown dwarfs yet discovered.

Named WISE J104915.57-531906, the system was identified by analysis of multi-epoch astrometry carried out by NASA’s Wide-field Infrared Survey Explorer (WISE). The discovery was made by associate professor of astronomy and astrophysics at Penn State’s Center for Exoplanets and Habitable Worlds Kevin Luhman. The system’s binary nature and follow up observations were confirmed by spectroscopic analysis carried out by the Gemini Observatory’s Multi-Object Spectrographs (GMOS).

Animation showing the motion of WISE 1049-5319 across the All-WISE, 2MASS & Sloan Digital Sky Survyies from 1978 to 2010. (Credit: NASA/STScI/JPL/IPAC/University of Massachusetts.) — Animation showing the motion of WISE 1049-5319 across the All-WISE, 2MASS & Sloan Digital Sky Surveys from 1978 to 2010. (Credit: NASA/STScI/JPL/IPAC/University of Massachusetts.)

This find is also the closest stellar system discovered to our own solar system since the discovery of Barnard’s star by astronomer E.E. Barnard in 1916. Incidentally, Barnard’s star was the center of many spurious and controversial claims of extrasolar planet discoveries in the mid-20^th century. Barnard’s star is 6 light years distant, and the closest star system to our own is Alpha Centauri measured to be 4.4 light years distant in 1839. In 1915, the Alpha Centauri system was determined to have a faint companion now known as Proxima Centauri at 4.2 light years distant. The Alpha Centauri system also made headlines last year with the discovery of the closest known exoplanet to Earth. WISE 1506+7027 is the closest brown dwarf to our solar system yet discovered. This also breaks the extended the All-WISE survey’s own previous record of the closest brown dwarf released in 2011, WISE 1506+7027 at 11.1 light years distant.

When looking for nearby stellar suspects, astronomers search for stars displaying a high proper motion across the sky. The very first parallax measurement of 11 light years distant was obtained by Friedrich Bessel for the star 61 Cygni in 1838. 61 Cygni was known as “Piazzi’s Flying Star” for its high 4.2” proper motion across the sky. To giving you an idea of just how tiny an arc second is, a Full Moon is about 1800” in diameter. With a proper motion of just under 3” per year, it would take WISE 1049-5319 over 600 years to cross the same apparent distance in the sky as viewed from the Earth!

An artist's conception of looking back at Sol from the binary brown dwarf system WISE 1049-5319, 6.5 light years distant. (Credit: Janella Williams, Penn State University). — An artist’s conception of looking back at Sol from the binary brown dwarf system WISE 1049-5319, 6.5 light years distant. (Credit: Janella Williams, Penn State University).

“Based on how this star system was moving in images from the WISE survey, I was able to extrapolate back in time to predict where it should have been located in older surveys,” stated Luhman. And sure enough, the brown dwarf was there in the Deep Near-Infrared Survey of the Southern Sky (DENIS), the Two Micron All-Sky Survey (2MASS) and the Sloan Digitized Sky Survey (SDSS) spanning a period from 1978 to 1999. Interestingly, Luhman also points out in the original paper that the pair’s close proximity to the star rich region of galactic plane in the constellation Vela deep in the southern hemisphere sky is most likely the reason why they were missed in previous surveys.

The discovery of the binary nature of the pair was also “an unexpected bonus,” Luhman said. “The sharp images from Gemini also revealed that the object actually was not just one, but a pair of brown dwarfs orbiting each other.” This find of a second brown dwarf companion will go a long way towards pinning down the mass of the objects. With an apparent separation of 1.5”, the physical separation of the pair is 3 astronomical units (1 AU= the Earth-Sun distance) in a 25 year orbit.

Size comparison of stellar vs substellar objects. (Credit: NASA/JPL-Caltech/UCB).

Brown dwarfs are sub-stellar objects with masses too low (below ~75 Jupiter masses) to sustain the traditional fusion of hydrogen into helium via the full proton-proton chain process. Instead, objects over 13 Jupiter masses begin the first portion of the process by generating heat via deuterium fusion. Brown dwarfs are thus only visible in the infrared, and run a spectral class of M (hottest), L, T, and Y (coolest). Interestingly, WISE 1049-5319 is suspected to be on the transition line between an L and T-class brown dwarf. To date, over 600 L-type brown dwarfs have been identified, primarily by the aforementioned SDSS, 2MASS & DENIS infrared surveys.

General location of WISE 1049-5319 in the constellation Vela. Note its proximity to the galactic plane. (Created by the author using Starry Night).

This discovery and others like it may go a long ways towards telling us how common brown dwarfs are in our region of the galaxy. Faint and hard to detect, we’re just now getting a sampling thanks to surveys such as WISE and 2MASS. The James Webb Space Telescope will do work in the infrared as well, possibly extending these results. Interestingly, Luhman notes in an interview with Universe Today that the potential still exists for the discovery of a brown dwarf closer to our solar system than Alpha Centauri. “No published study of the data from WISE or any other survey has ruled out this possibility… WISE is much more capable of doing this than any previous survey, but the necessary analysis would be fairly complex and time consuming. It’s easier to find something than to rule out its existence.” Said Luhman. Note that we’re talking a nearby brown dwarf that isn’t gravitationally bound to the Sun… this discussion is separate from such hypothetical solar companions as Nemesis and Tyche…and Nibiru conspiracy theorists need not apply!

The WISE 1049-5319 system is also a prime target in the search for nearby extra-solar planets. “Because brown dwarfs have very low masses, they exhibit larger reflex motions due to orbiting planets than more massive stars, and those larger reflex motions will be easier to detect.” Luhman told Universe Today. Said radial surveys for exoplanets would also be carried out in the IR band, and brown dwarfs also have the added bonus of not swamping out unseen planetary companions in the visible spectrum.

Congrats to Mr. Luhman and the Center for Exoplanets and Habitable Worlds on the discovery. You just never know what’s lying around in your own stellar backyard!

Read this original discovery paper here.