Artist’s concept of NASA’s Dawn spacecraft at Ceres. (Dawn/NASA)

On March 6, NASA’s Dawn will become the first spacecraft to encounter a dwarf planet when it arrives at Ceres, the first (and largest) object discovered in the Main Asteroid Belt between the orbits of Mars and Jupiter.

In January, NASA released  these images of Ceres, pictures that clearly show its round and planet-like shape, and even some surface features. The pictures were taken from a distance of 147,000 miles, a little more than half the distance from the Earth to the Moon.

On February 4, from a distance of 90,000 miles, Dawn took a series of images that were made into an animation with the best resolution yet: 8.5 miles per pixel.

Ceres holds a lot of mysteries for us. For the better part of the two centuries since its discovery in 1801, we knew little more than its approximate size (590 miles in diameter), and only recently its generally spherical shape. Until recent observations by the Hubble Space Telescope, Ceres appeared through telescopes as little more than a blurry smudge.

These new clues are tantalizing. Ceres appears to be composed of a rocky core surrounded by an icy mantle, and has been observed to exude gases into space, not unlike comets do as they approach the sun. It has even been speculated that Ceres could possess a sub-surface ocean of liquid water. Far from being a sterile, dry mountain of rock, as most asteroids are envisioned, Ceres has already exhibited some planet-like, or at least dwarf-planet-like, characteristics.

Best views of Ceres to date, January 2015. (Dawn/NASA)

What makes Ceres a dwarf planet and not just a very large asteroid, as it was classified for decades prior to the 2006 creation of the dwarf planet classification?

1. Ceres is round–spherical. It has to be round to be considered a planet or a dwarf planet. This is one of the qualifying factors of planethood: to be large enough and have sufficiently strong gravity to be pulled into a spherical shape. Smaller objects—comets and asteroids—fail this mark because the strength of their rock and ice structures overpower their weak gravitational pull.

2. Ceres orbits the sun directly–you can’t be a planet or a dwarf planet if you don’t. There are moons in the solar system much larger than Ceres, and as round as any planet. In fact, if a moon like Ganymede or Callisto or Titan orbited the sun directly instead of orbiting a planet, it would probably be classified as a planet itself. Ganymede and Titan, in fact, are larger than the planet Mercury.

If you meet these two criteria, you are eligible for dwarf planet status.

On March 6, when Dawn arrives, we may not see many images right away. Dawn will make its final approach from the side of Ceres opposite the sun, so will only be able to view its dark side. But after the spacecraft settles down, in mid-April, Dawn will begin to observe the dwarf planet’s illuminated side, and from a distance of 14,000 miles the resolution of the pictures it will send back will be fourteen times greater than those of the Hubble Space Telescope.

Artist illustration of the Kepler spacecraft. (Ames Research Center, JPL-Caltech, T. Pyle/NASA)

Space exploration has suffered its share of setbacks and disappointments over the decades, but few of them stung as much as the 2013 mechanical failure of the Kepler spacecraft, a space telescope designed to accomplish one of the most exciting explorations of space ever: the search for potentially Earth-like planets orbiting other stars.

The Kepler spacecraft is basically a giant, very sensitive telescopic camera designed to compete in an ultimate cosmic staring contest: to gaze continuously at a patch of about 150,000 stars near the constellation Cygnus, and wait for them to blink—that is, dim slightly—when planets they might possess pass briefly in front of them.

To find Earth-like extrasolar planets, Kepler had to do more than detect the very slight dimming of starlight caused by the transit of relatively small, Earth-sized worlds. It had to find the ones orbiting within their star’s “habitable zone,” or “Goldilocks zone:” the distance at which conditions on the planet are neither too hot nor too cold to support that commodity essential to all life on Earth, liquid water–the “porridge of life,” one might say.

At that distance from its star, a planet only orbits every few months, or even years, so for Kepler to confirm their existence requires it to make continuous observations for several years, so as not to miss any transits. To win the contest, Kepler could not blink.

But in 2013, Kepler lost one of the stabilizing reaction wheels that allowed it to point at its target star field in the constellation Cygnus. This malfunction ended its mission to look for Earth-sized planets among those stars. And though Kepler confirmed the existence of hundreds of exoplanets—some of them of Earth-stature and orbiting within their habitable zones–during its nearly four-year primary mission, the curtailing of this exploration of extraterrestrial Earths was a soul-crushing event for scientists, if not all of us. How much more might we have learned about the worlds Kepler discovered? How many more might have been found?

But just when it seemed that the Kepler storybook had been slammed shut after only the first chapter or two, human imagination stepped in to envision how the crippled spacecraft could be repurposed for a new mission: Kepler 2.

With its two remaining functional reaction wheels and a strategic positioning of the spacecraft so that the tiny amount pressure exerted by sunlight itself is balanced, Kepler can stabilize and point to the ring of sky around the ecliptic—the plane that the planets of our solar system occupy—and last June began a new career of observation in this mode.

To prevent the gradual intrusion of the sun into Kepler’s field of view, Kepler 2 will be able to observe a target patch of sky along the ecliptic for about 83 days before needing to point to another spot away from the sun. But during these 83 day “observing campaigns,” Kepler will bring the full force of its powerful instrumentation to bear on the objects it observes.

So, the staring game is back on, even if the rules have changed a bit and Kepler has to blink occasionally. But the exoplanetary adventure is far from over…

Corn plants struggle to survive in a drought-stricken farm field near Oakton, Indiana. The corn and soybean belt in the middle of the nation is experiencing one of the worst droughts in more than five decades.
(Scott Olson/Getty Images)

By Andrea Thompson
Climate Central

The warmth that led 2014 to become the hottest year on record has continued into 2015, with last month ranking as the second-hottest January on record globally, the National Oceanic and Atmospheric Administration announced Thursday.

“I think it is safe to say that the warmth so far in 2015 really is a continuation of the warmth in 2014,” NOAA climatologist Jake Crouch said in an email.

The past month was 1.39°F above the 20th century average of 53.6°F,  second only to 2007 in the agency’s records, which go back to 1880. The Japan Meteorological Agency had January 2015 tied with both January 2002 and 2007, while NASA data put the month in a tie for third with 2002, behind 2007 as the hottest and 2005 and 2013 as the second hottest.

Different agencies handle global temperature data in slightly different ways, leading to small differences in monthly and yearly global temperature rankings.

All three agencies ranked 2014 as the warmest year on record by a slim margin, driven by the accumulation of heat-trapping greenhouse gases in the atmosphere. Nine of the 10 hottest years on record have all occurred in the 21st century, with the exception of the blockbuster El Nino year of 1998. There hasn’t been a record cold year set since 1911, while during the same period there have been 19 record-warm years, according to a Climate Central analysis.

“There’s a lot of warmth in the ocean,” NOAA climatologist Michelle L’Heureux said. Considering that the map shows such anomalous heat even compared to the past 30 or so years, when the signature of global warming had already emerged makes those rankings even more remarkable, she said.

The oceans on the whole were the third hottest on record for January 2015, according to NOAA. Record ocean warmth was seen off both coasts of North America; the hot waters off the West Coast has helped reinforce the unseasonably high temperatures and dry conditions in that part of the U.S.

Other ocean areas were much warmer than normal, though there were some cool spots, most notably in the North Atlantic between Greenland and Europe where record-cold sea surface temperatures were recorded.

How global temperatures shape up over the rest of the year remains to be seen, but the ocean tends to hang on to heat for much longer than land areas, which will keep temperatures elevated for awhile. And as carbon dioxide and other greenhouse gases continue to be emitted, the dice will be loaded to warmer and warmer years in the future.

Climate Central is an independent organization that researches and reports on climate change.

Artist’s concept of NASA’s Dawn spacecraft arriving at Ceres. (Dawn/NASA)

Early this morning, at about 4:39 AM Pacific Time, NASA’s Dawn spacecraft arrived at Ceres, making history as it swung into orbit around the dwarf planet. Dawn left Earth eight years ago, headed for the Asteroid Belt, located between Mars and Jupiter. The spacecraft spent a year photographing the asteroid Vesta, and then two-and-a-half years on the journey to its final port-of-call.

Over the last several months, scientists and the public have been growing steadily more excited as Dawn sent back photos of an ever-closer Ceres. For the average space enthusiast, Dawn’s arrival feels like the discovery of a new world.

We’ve known Ceres existed since 1801, when it was discovered by Giuseppe Piazzi. But for scientists, this encounter means far more than seeing a mysterious object up close for the first time.

“Ceres has the potential to turn some of our old ideas about how planets formed completely upside down,” says Dr. Britney Schmidt, Assistant Professor at Georgia Institute of Technology’s School of Earth and Atmospheric Sciences. “If Ceres turns out to be icy in its interior, this would not only tell us that there were potentially lots of icy asteroids, but also that some of the ‘classical’ assumptions about the timing of planetary formation could be wrong.”

Ceres is an example of a “protoplanet,” an object that formed early in the solar system’s history by accumulating smaller chunks of rock and ice and snowballing toward a planet-stature object—or at least a major building-block of another planet. But Ceres’ development was arrested, and it has remained more or less unchanged from three or four billion years ago.

“Even though [Ceres] is likely refrozen now,” Schmidt says, “with the gravity data from Dawn, we may be able to show that Ceres at one time had a subsurface ocean.”

Dawn’s leisurely approach over the past months has supplied us with a constant feed of images that have grown ever sharper and more detailed, peeling away layers of fuzzy mystery like the skin of an onion, and revealing new mysteries in the process. That’s something astronomers are happy about, like getting an unexpected dividend on your investment. Mystery, after all, inspires science.

Image sequence of Ceres taken by the Dawn spacecraft. (Dawn/Nasa)

A week before Dawn’s arrival, NASA whetted our appetites for the adventure by publishing a picture that revealed two small white spots nestled close together in a crater—and told us that the nature of the roughly Lake Tahoe-sized feature was as yet unknown.

What are these spots? Kids visiting Chabot Space & Science Center had some truly bright ideas, including giant pieces of reflective metal, huge chunks of ice, volcanoes, and, yes, aliens.

Dawn’s previous subject of interest, Vesta, can also be classed as a protoplanet like Ceres, though Vesta was found to be composed mostly of rock. Ceres, on the other hand, may be as much as 25% water ice. In terms of the protoplanet accretion processes that formed the Earth, it is thought that dry Vesta-type objects may have built up Earth’s rocky core and mantle, while icy “wet” protoplanets like Ceres may have contributed to the formation of our oceans. Certainly, Dawn’s investigations in the Asteroid Belt have shown that the kitchen in which Earth was cooked up was stocked with both ingredients.

This cutaway illustration of Saturn’s moon Enceladus shows a subsurface ocean with hydrothermal activity, where water interacts with heat deep inside the moon, and erupts through the surface in plumes of vapor. (Cassini/NASA)

It’s an exciting time to be an astrobiologist looking for life beyond Earth, with signs of water spouting up all over the solar system. In the latest example, NASA’s Cassini spacecraft has delivered clear evidence that, far beneath the icy crust of Saturn’s small moon Enceladus, hydrothermal activity may be at work, similar to what we find in some life-friendly environments on Earth.

That makes three leading contenders for bodies in our solar system that possess life-friendly conditions.

Jupiter’s moon Europa hides under its icy crust what may be the largest ocean in the solar system, and there has been a renewed interest in mounting a mission to explore it.

And NASA’s Curiosity rover continues to quench our thirst for finding signs of liquid water in Mars’ distant past. Curiosity is currently prospecting the water-deposited sedimentary layers on Mount Sharp, left behind by ancient surface seas.

Water vapor plumes erupting from Saturn’s moon Enceladus. (Cassini/NASA)

It has been a decade since Cassini first captured images of plumes of material erupting from great fissures in the icy crust of Enceladus, material that it later identified as water mixed with smaller amounts of nitrogen, methane, and carbon dioxide. These plumes told us there was liquid water beneath the surface. We thought at the time that the water may be held in some kind of geyser chamber heated and pressurized by tidal energy supplied by Saturn’s gravity.

Over its decade of exploration Cassini’s Cosmic Dust Analyzer (CDA) instrument has also repeatedly detected microscopic solid particles flying about the Saturn system. Researchers have identified the particles as silica grains — the same material found in sand and quartz.

The very consistent sizes of the particles (the largest between 6 and 9 nanometers) has led scientists to conclude that they were produced by a very specific process: hot, alkaline liquid water super-saturated with minerals experiencing a sudden and drastic drop in temperature. Where, it was asked, might these conditions exist in the Saturn system, and by what mechanism would the silica grains be delivered into space, where Cassini detected them? Enceladus, with its liquid water ocean and water vapor plumes spraying into space, satisfies both of these questions.

Similar conditions exist here on Earth. On the floor of our ocean, usually at the boundaries of crustal plates, are found hydrothermal vents. These are underwater hot springs formed when seawater, percolating into the ocean floor, comes into contact with hot magma. Plumes of hot water erupt through vents in the ocean floor, carrying dissolved minerals. Some of those minerals solidify on contacting cold ocean water.

White smokers — hydrothermal vents on Earth’s ocean floor (NOAA)

The mineral structures that build up around the vents, along with the smoke-like plumes that spout from them, are called “black smokers” and “white smokers.” Black smokers form around hotter hydrothermal vents, and get their black color from iron monosulfide. The less common white smokers form around cooler vents, their white color coming from chemicals like barium, calcium, and silicon.

These deep ocean smokers create environments that support life: communities of organisms sustained entirely by heat and chemical energy coming from Earth’s interior, no sunlight required! And though the life forms found around the vents probably originated from Earth’s sunlit surface, this does not rule out a genesis scenario where life might originate within such an environment.

And that’s where Cassini’s discovery gets really exciting.

Analysis of the silica grains detected by Cassini indicate that hydrothermal activity similar to that on Earth is taking place on the floor of Enceladus’ ocean, where water, under great pressure at depth, interacts with heat and minerals emerging from the moon’s interior. For the hydrothermal vents to produce these particular silica grains, the temperatures must be at least 194 degrees Fahrenheit. If not super-hot black smokers, might Enceladus have something like our own white smokers going on?

The possibilities are tantalizing. Finding even one microbe out there would, in an instant, resolve one of the most profound scientific, philosophical, and human questions of all time: are we alone? That question was once phrased, “Is there life out there?” These days, it’s starting to sound more like, “How many places will we find it?”

NASA’s MESSENGER spacecraft spiraling toward the surface of its 10-year study, planet Mercury. (Johns Hopkins University Applied Physics Laboratory/Carnegie Institute of Washington/NASA)

When is the last time you thought of the planet Mercury? That smallest of planets, closest to the sun and ever hiding behind the skirts of dawn or dusk, is easy to overlook—out of sight, out of mind.

But Mercury has been on scientists’ minds for some time now and subjected to close scientific scrutiny by NASA’s MESSENGER spacecraft for the better part of a decade.

Mercury is a world of wonderful extremes. It is the closest planet to the sun, the smallest planet of the solar system, and also one of the densest.

In fact, owing to its density, tiny Mercury’s surface gravity is about equal to that of the larger Mars. It is thought that as much as 75% of Mercury’s radius may account for a very large, iron-rich core.

Artist impression of a “rupes” (cliff), or “lobate scarp,” on Mercury. These scarps were uplifted as Mercury cooled and contracted. (Michael Carroll, the Johns Hopkins University Press)

Mercury experiences day and night temperature swings ranging from colder than -300 to hotter than 800 degrees Fahrenheit–the largest range in the solar system.

Named for the Roman messenger god, Mercury is the speediest planet, zipping around the sun in only 88 days at speeds ranging from 24 to 36 miles per second.

And, in stark contrast to this short orbital period, Mercury’s slow rotation of 176 Earth days makes for very, very long days and nights.

But for all of its fascinating characteristics and its relative closeness to us, Mercury had been one of the least explored planets of the solar system, receiving only three fleeting flybys by the Mariner 10 spacecraft in 1974, which revealed to us only half of the planet’s surface, and gave us the impression that Mercury might be very similar to Earth’s Moon.

NASA’s “MErcury Surface, Space ENvironment, GEochemistry, and Ranging” (obviously, someone at NASA really wanted this acronym to spell out “MESSENGER”) spacecraft finally gave us a better look a decade ago when it arrived at Mercury, revealing that the resemblance to our Moon is truly only skin deep.

Unlike our lightweight Moon, Mercury possesses a massive iron core, and currents within its molten portion generate a strong global magnetic field, not unlike Earth’s protective magnetosphere. Mercury’s surface composition is also quite different, its surface rocks containing far less iron and far more sulfur than the Moon. And though both Moon and Mercury are covered with impact craters (the main reason for their superficial resemblance), Mercury also possesses an abundance of “lobate scarps,” a telltale geographic feature formed by global contraction.

However, because Mercury’s axial tilt is nearly zero, conditions at its poles, particularly at the bottom of crater floors, do harbor pockets of permanent shadow, in which ice could persist—and there is compelling evidence of significant ice deposits.

MESSENGER will soon deliver its final message to us. Its rocket propellant tanks nearly depleted after years of orbital maneuvering, NASA has engaged this spacecraft in a so-called “hover” campaign, in which MESSENGER is descending closer and closer to Mercury’s surface and obtaining the highest resolution imagery and other data of its entire mission.

NASA’s plan is to get every last bit of science out of MESSENGER as it descends, until the moment that it impacts Mercury’s surface and decisively ends its mission in a flourish of fireworks that no one will see.

When it collides with Mercury’s surface, MESSENGER will have joined a very small “club” of spacecraft from Earth that have physically contacted other bodies in the cosmos.

This “Touchdown Club” includes: numerous robotic and human-crewed spacecraft that have landed on the Moon; a large and growing number of landers and rovers that have set down (intact or in pieces) on Mars; a similarly decorated corps of heat-resistant robots on Venus; the Galileo spacecraft, which first sent an atmospheric probe into Jupiter’s cloudtops, and then added itself to this short list in an end of mission flame-out; Cassini’s Huygens probe on Titan; the NEAR spacecraft on the asteroid Eros; and finally, and most recently, the partially successful landing of Europe’s Philae probe on comet Churyumov-Gerasimenko.

Good luck, and farewell, MESSENGER!

Artist concept of Kepler 186f, an Earth-sized exoplanet within its star’s habitable zone. (NASA Ames/SETI Institute/JPL-Caltech)

Faint planets orbiting distant stars are by nature challenging to find, and long eluded detection. But since 1992, when Polish astronomer Aleksander Wolszczan first confirmed the existence of an extrasolar planet, the numbers we’ve found have snowballed.

Now, NASA’s next-step missions aimed at understanding the Milky Way’s apparent abundance of worlds are on the horizon. The Transiting Exoplanet Survey Satellite (TESS) and James Webb Space Telescope (JWST) promise to be powerful tools in the discovery of new exoplanets, and will allow us to study their physical characteristics in far greater detail.

Not surprisingly, the first exoplanet discoveries were of gas giant planets like Jupiter and Saturn — planets that orbit close to their stars so their telltale influences are more pronounced, and easier to detect.

The Search for Planets A Bit Like Earth

On March 7, 2009, NASA’s Kepler spacecraft launched on an ambitious campaign to search for Earth-sized exoplanets orbiting their stars at moderate distances. That is, distances where conditions are right to support the presence of liquid water, the indispensable elixir of life as we know it (that is to say, Earth life).

Before a series of unfortunate mechanical failures in 2012 and 2013, Kepler focused on a narrow patch of sky near the constellation Cygnus, observing stars ranging from a couple hundred to almost 8,000 light years away from Earth.

The evolution of NASA’s exoplanet missions. (NASA/TESS)

To date, astronomers have confirmed a total 1,827 exoplanets, more than a thousand of them detected by Kepler. And there are more than 4,600 Kepler candidates still awaiting confirmation — impressive results for only a few short years of observations.

In total, about 30 exoplanets, all between one and two times the size of Earth, have been ranked as potentially habitable planets!

With Kepler partially on the fritz (though reinstated as Kepler 2.0, and now on a mission adapted to its handicapped status), we can look to NASA’s TESS and JWST missions to advance us to the next step in our exploration of exoplanets.

Looking Closer to Home

TESS, scheduled for launch in 2016, will cast its eye closer to home than Kepler. Where Kepler observed a narrow, cone-shaped swatch of the Milky Way galaxy extending thousands of light years, TESS will target stars that are 30 to 100 times brighter — and consequently, mostly closer to us — than Kepler’s subjects.

Left: Currently known planets orbiting stars with a certain brightness. Right: Same as left, plus, in red, the number of exoplanets scientists expect TESS may discover. (TESS/NASA)

One of Kepler’s revelations was that the most common type of exoplanet is between one and two times the size of Earth.  Science fiction stories dating back many decades preferred these Earth-style planets over gas giants like Jupiter or diminutive dwarfs like Pluto; the planets usually hosted characters who needed solid ground to stand on, and temperate, breathable air to sustain them. Science looks to Earthy exoplanets as the most likely places to find signs of life. How exciting to learn that both science and science fiction have been rewarded for their visions!

Kepler’s exo-Earth finds, however, mostly orbit distant and often faint stars. So beyond being a good source of statistical data that has informed us of the abundance of exoplanets in our galaxy, there’s been little opportunity to follow up with more detailed measurements or characterization of their physical properties. In most cases, they’re just too far away to tell us much more than their approximate sizes and orbital periods.

TESS, on the other hand, should yield a catalog full of transiting exoplanets located around the brightest and nearest stars in the galaxy — close enough for large telescopes, on the ground and in space, to conduct follow-up analysis.

What Are Exoplanets Made Of?

JWST, the infrared-wavelength successor to the Hubble Space Telescope, is scheduled for launch in 2018 and will be a powerful tool in exoplanet investigation. Not only will the JWST study exoplanets by the conventional measurements of star-wobble and exoplanet transits, but unlike Kepler and most other observatories, this space telescope will make direct observations of exoplanets.

Only some six decades ago, we didn’t even have a good understanding of what nearby planets like Venus, Mars, and Jupiter are like. Now, we’re examining planets many light years away, in other star systems, with enthusiasm, hopeful expectation and burgeoning imagination.

Curiosity’s self-portrait at “Mojave” on Mount Sharp. (NASA/JPL-Caltech/MSSS)

The 1964 science fiction classic, “Robinson Crusoe on Mars,” paraphrased an old adage, “Water is where you find it.” NASA’s exploration of the real Mars has paraphrased further, “On Mars, water seems to be where you look for it!”

Intensive exploration of Mars by NASA spacecraft continues to pay tantalizing dividends in our quest for signs of liquid water, and the potentially life-friendly environments it could offer. Here are a few recent finds by the Curiosity rover, and other spacecraft.

Mineral Veins of Garden City

Recently, NASA’s Curiosity rover discovered a mineral formation that drew the eye of mission water-seekers. Criss-crossing the bedrock of a site named Garden City are raised veins of whitish material, marbled through the rock in a very particular pattern.

Mineral veins found by NASA’s Curiosity rover on Mount Sharp. (NASA/JPL-Caltech/MSSS)

On Earth, similar formations of mineral veins lacing through rock are created when water, flowing through cracks, deposits minerals. In Garden City on Mars, erosion of the surrounding rock has exposed the veins, forming small ridges as high as 2.5 inches and an inch or so wide.

Upon closer examination, the veins were found to be two-shaded, with darker material at the edges sandwiching a lighter layer between. This indicates a process that involved different liquid water solutions depositing different minerals at different times.

Curiosity, as well as the veteran rover Opportunity, had found outcroppings of likely water-formed calcium sulfate in other locations, but the two-tone veins at Garden City offer a more detailed glimpse into the story of how the environment, at least locally, may have changed long ago.

As Curiosity continues its climb up the slopes of Mount Sharp, exploring ever-younger layers of sediment, a more complete picture of how the apparently watery Mars of long ago became the dry desert world we know today will develop.

Martian Mud?

While most of Curiosity’s instrumentation is geared to study the chemistry and morphology of the Martian soil and rock, atmospheric data collected by its Rover Environmental Monitoring Station (REMS) has produced a fascinating watery possibility as well.

For more than a year, REMS has measured atmospheric temperature and relative humidity in the lower region of Gale Crater where Curiosity is exploring. From these measurements, along with the previous detection of perchlorate salts in more than one location on Mars, a theory has developed suggesting that liquid water on Mars’ surface isn’t necessarily a thing of the distant past.

As the theory goes, under the right conditions of temperature and relative humidity, salty minerals like perchlorate, which draw in surrounding water vapor from the air, can form a liquid brine in the soil—most likely at night when temperatures drop. Overnight brine moisture would evaporate under the sun’s rays after dawn, but for a time the mixture would form a substance that might be characterized as “Martian mud….”

Flows of material running down the slopes of crater walls on Mars, captured by NASA’s Mars Reconnaissance Orbiter. (NASA/JPL-Caltech/Univ. of Arizona)

Though Gale Crater, located near the planet’s equator, is one of Mars’ least likely climates for brine-forming conditions, Curiosity’s observations suggest that small amounts could form for short periods. In Mars’ higher latitudes, where atmospheric relative humidity is greater and sunlight less intense, the conditions are more favorable. In fact, overnight brine accumulation is a leading contender to explain downhill flows of material observed by the Mars Reconnaissance Orbiter spacecraft on high-latitude steep slopes.

Ready-to-eat Nitrogen

Another recent detection made by Curiosity is that of “ready to eat” nitrogen—so to speak. Though this detection does not pertain to water, it is of possible relevance to the same ultimate goal of Mars exploration: detection of life-friendly environments on Mars.

This time it was SAM’s time to tell the story—SAM, the Sample Analysis at Mars instrument. SAM detected nitric oxide (a molecule of one nitrogen and one oxygen atom) in a collected soil sample. The nitric oxide is thought to have been released when nitrates in the sample broke down as it was heated—and in any case, this marks the first discovery of “biologically useful” forms of nitrogen on Mars.

Nitrates in general are nitrogen-bearing molecules of a form that living organisms can make use of in the life process. In Earth life, obtaining nitrogen from the environment is crucial, since it is an essential element of such important molecules as DNA and RNA, among other things. Though nitrogen is abundant in Earth’s atmosphere, making up 79% of it, most of it is in the form of nitrogen gas, a molecule of two very tightly bound nitrogen atoms. Most life forms on Earth cannot make use of nitrogen in this form, though certain organisms can break it apart and convert it to usable forms, and in doing so introduce nitrates into the food chain.

Scientists don’t believe that the nitrates found in Mars’ soil were produced by biological activity, but rather by non-biological processes, probably long ago in Mars’ past. Energetic events like meteorite impacts and lighting strikes are two possible nitrate-forming agents.

Whatever the source, the fact that nitrogen in a form that Earth-organisms would “eat up” is present adds to the preponderance of evidence that Mars once had a habitable environment.

Whether anything actually inhabited Mars is still an open question, but one actively being pursued by missions like Curiosity.

Diagram of the Milky Way galaxy showing the distances to known extrasolar planets. (JPL-CalTech/NASA)

We’ve recently discovered one of the most distant extrasolar planets known to date. Or rather, NASA’s Spitzer Space Telescope and Poland’s Optical Gravitational Lensing Experiment (OGLE) have.

Extrasolar planets (exoplanets) are planets that orbit stars other than our sun, and in the past two decades we have detected over 1,800 of them. Most of these alien worlds belong to stars in our galaxy that are relatively close to our solar system, but scientists have used different techniques for detecting and studying exoplanets at greater distances.

The newly discovered exoplanet, called OGLE-2014-BLG-0124L, has about half the mass of Jupiter and orbits a star 13,000 light years from Earth, close to the crowded, star-rich central core of our galaxy.

The observing campaign to find and study far-flung exoplanets like this one is aimed at giving us a clearer understanding of the distribution of exoplanets across the galaxy, and insight into the conditions under which planetary systems form.

Computing the Exoplanet’s Distance

OGLE and Spitzer made the detection through “gravitational microlensing” observations, which take advantage of the situation when a star passes between us and another star.

Diagram of a star and planet focusing the light of a more distant star toward on observer on Earth.

Just as a telescope’s glass lens bends and focuses light to produce a brighter image of a distant object, a star’s gravity can do the same trick, but on a much grander scale.

When a star passes between us and a more distant star, its gravity can bend and focus the farther star’s light, causing a temporary increase in its brightness. If there happens to be a planet orbiting the intermediate star, its light also may be magnified and detected.

Measuring the distance to this far-off exoplanet was accomplished by comparing observations made by an Earth-based OGLE telescope and NASA’s Spitzer, which orbits the sun far from Earth.

By noting the difference in the times of the lensing event as observed by OGLE and Spitzer, scientists were able to triangulate the distance of 13,000 light years—or 78 quadrillion miles! And by pinpointing the distance, the estimate of the exoplanet’s half-Jupiter mass was also possible.

Polling the Galactic Core

Polling the population of exoplanets in the star-dense region of the galactic core adds to our knowledge of exoplanets both near and far, providing data to help answer questions like: are exoplanets more or less common in the galactic core, versus the spiral arms where our solar system resides? Scientists seek to explore how planetary formation may be influenced by a star system’s location in the galaxy, so the more we know about the nature of exoplanetary systems in different regions, the better.

A gravitational lens of a much greater scale: a giant elliptical galaxy focusing the light of a more distant galaxy into a ring shape. (HST/NASA)

Microlensing detections made by a single observatory cannot always yield much more than an exoplanet’s presence. A very distant star detected with this technique isn’t normally visible, making the determination of its exact distance (and that of any planets it may possess) difficult to impossible. Of the 30 exoplanets detected through gravitational microlensing, the farthest being 25,000 light years away, we know the distance to only about half of them.

Another factor in this type of observation is the chance nature of the star crossings, which we can only observe once for any given pair of stars. So, we may have only one chance to make a planet detection, with no possible follow-up observations. Still, the far greater concentration of stars in and near the galactic core provides many more star crossings and opportunities to make exoplanet detections.

Exoplanets Closer to Home

Closer to home, the more common techniques for finding exoplanets—either by measuring the wobble of a star caused by an orbiting planet or the dimming of its light when a planet transits in front of it—has yielded over 1800 confirmed worlds, mostly orbiting stars much closer to our solar system’s neighborhood.

NASA’s Kepler space telescope, which pursues exoplanets using the transit method, is responsible for the bulk of those finds, as well as most of the detections of Earth-sized planets.

At least 65 exoplanets have been confirmed within 50 light years of Earth—close enough for the television and radio transmissions that we began broadcasting in the middle of the 20th century to have reached. As of next year, in fact, the first broadcasts of Star Trek (the original series) will have reached all 65 of these closest exoplanets!

As for the prospects of visiting any of these exoplanets in person—well, that may take a while. The closest known exoplanet, which orbits the nearest star to our solar system, Alpha Centauri, is 4.36 light years away, or 26.16 trillion miles, a distance that would take the fastest spacecraft we’ve ever flown almost 60,000 years to reach.

Artist concept of New Horizons flyby of Pluto. (Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

Eighty-five years after its discovery in 1930, the distant and mysterious Pluto will finally become an “explored” planet.

NASA’s New Horizons spacecraft has been en route to Pluto for nearly ten years, and is almost there, speeding toward a close encounter on July 14.

As of late May, New Horizons was less than 35 million miles from its target–roughly the same distance from the sun to the planet Mercury.

In December, the small, nuclear-powered interplanetary probe awoke from a state of robotic hibernation to make ready for the flyby. Since waking, mission operators have performed systems tests and captured approach images of the Pluto system from a distance.

The upcoming flyby encounter is a proverbial “don’t blink or you’ll miss it” scenario, so making sure that all systems are go is imperative.

Though the “big reveal” will take place on July 14, New Horizons has been tantalizing us with advances on our investment of curiosity. Here are a few highlights from recent weeks:

What We Know About Pluto and Its Moons

Images captured by New Horizons’ LORRI instrument showing mutual revolution of Pluto and Charon. (NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

A series of images captured by New Horizons’ Long-Range Reconnaissance Imager (LORRI) instrument shows us clearly what we have known analytically for some time: that Pluto and its largest moon, Charon, are more of a double-planet than a planet and its moon.

Charon is half the diameter of Pluto, so large in comparison that the two actually orbit a point in space between them, like a pair of figure skaters swinging each other by the hands as they spin.

New Horizons captures images of all known moons of Pluto with its Long Range Reconnaissance Imager instrument. (NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

New Horizons has captured images of Pluto’s five known moons, one by one. First was the large moon Charon, which it spotted almost two years ago.

Two smaller moons, Hydra and Nix, came into view in July 2014 and last January.

Finally, in late April/early May, the two smallest and faintest known satellites, Kerberos and Styx, were revealed, completing the family portrait.

If there are more moons orbiting Pluto, New Horizons is well-positioned to discover them as it draws closer.

A Polar Ice Cap on Pluto?

In late April, from a distance of 70 million miles, New Horizons began to capture images of surface features on Pluto, including a bright spot located at Pluto’s visible pole. It’s too soon to tell, but a bright area at a planet’s pole is suggestive of a polar ice cap, as on Earth and Mars.

These images prove that New Horizons has begun to show us things we’ve never seen before–things we cannot presently see from Earth.

When New Horizons launched in 2006, it set forth to explore the smallest, most distant, and least understood planet in the solar system. Despite the fact that the International Astronomical Union reclassified Pluto as a dwarf planet shortly after launch, our scientific and imaginative curiosity about this small world is unchanged.

In fact, one of the reasons that Pluto was reclassified is that it is different from the major planets, and more similar to other objects found orbiting the sun beyond Neptune’s orbit.

Representative of a little-understood group of celestial bodies, the “ice dwarf planets,” one of four discovered so far, the exploration of Pluto and its moons is a first look into a realm of our solar system that we know almost nothing about.

Since childhood, I—along with millions of others—have dreamed about what Pluto may be like, envisioning a dark, icy landscape glittering under the weak rays of a sun no brighter than an exceptional star. That long dream is almost over–and my excitement is hard to contain!