NASA Selects Investigations for Future Key Planetary Mission
Artist's concept of the Psyche spacecraft, a proposed mission for NASA's Discovery program that would conduct a direct exploration of an object thought to be a stripped planetary core. Credit: NASA/JPL-Caltech
In their drive to set exploration goals for the future, NASA’s Discovery Program put out the call for proposals for their thirteenth Discovery mission in February 2014. After reviewing the 27 initial proposals, a panel of NASA and other scientists and engineers recently selected five semifinalists for additional research and development, one or two of which will be launching by the 2020s.
With an eye to Venus, near-Earth objects and asteroids, these missions are looking beyond Mars to address other questions about the history and formation of our Solar System. Among them is the proposed Psyche mission, a robotic spacecraft that will explore the metallic asteroid of the same name – 16 Psyche – in the hopes of shedding some light on the mysteries of planet formation.
Discovered by Italian astronomer Annibale de Gasparis on March 17th, 1852 – and named after a Greek mythological figure – Psyche is one the ten most-massive asteroids in the Asteroid Belt. It is also the most massive M-type asteroid, a special class pertaining to asteroids composed primarily of nickel and iron.
For some time, scientists have speculated that this metallic asteroid is in fact the survivor of a protoplanet. In this scenario, a violent collision with a planetesimal stripped off Psyche’s outer, rocky layers, leaving behind only the dense, metallic interior. This theory is supported by estimates of Psyche’s bulk density, spectra, and radar surface properties; all of which show it to be an object unlike any others in the Belt.
Promotional artwork for the proposed Psyche mission. Credit: Peter Rubin/JPL-CALTECH.
In addition, this composition of 16 Psyche is strikingly similar to that of Earth’s metal core. Given that astronomers think that larger planets like Venus, Earth and Mars formed from the collision and merger of smaller worlds, Psyche could be the remains of a protoplanet that did not get to create a larger body.
Had such a planetesimal been struck by a large enough object, it would have been able to lose its lower-mass exterior while keeping its core intact. Thus, studying this 250 km (155 mile) wide body, offers a unique opportunity to learn more about the interiors of planets and large moons, whose cores are hidden beneath many miles of rock.
Dr. Linda Elkins-Tanton of Arizona State University’s School of Earth and Space Exploration is the Principle Investigator of this mission. As she and her team stated in their mission proposal paper, which was originally submitted as part of the 45th Lunar and Planetary Science Conference (2014):
“This mission would be a journey back in time to one of the earliest periods of planetary accretion, when the first bodies were not only differentiating, but were being pulverized, shredded, and accreted by collisions. It is also an exploration, by proxy, of the interiors of terrestrial planets and satellites today: we cannot visit a metallic core any other way.
“For all of these reasons, coupled with the relative accessibility to low- cost rendezvous and orbit, Psyche is a superb target for a Discovery-class mission that would characterize its geology, shape, elemental composition, magnetic field , and mass distribution.”
The huge metal asteroid Psyche may have a strong remnant magnetic field. Credit: Damir Gamulin/Ben Weiss
A robotic mission to Pysche would also help astronomers learn more about metal worlds, a type of solar system object that scientists know very little about. But perhaps the greatest reason to study 16 Psyche is the fact that it is unique. So far, this body is the only metallic core-like body that has been discovered in the Solar System.
The proposed spacecraft would orbit Psyche for six months, studying its topography, surface features, gravity, magnetism, and other characteristics. The mission would also be cost-effective and quick to launch, since it is largely based on technology that went into the making of NASA’s Dawn probe. Currently in orbit around Ceres, the Dawn mission has demonstrated the effectiveness of many new technologies, not the least of which was the xenon ion thruster.
The Psyche orbiter mission was selected as one of the Discovery Program’s five semifinalists on September 30th, 2015. Each proposal has received $3 million for year-long studies to lay out detailed mission plans and reduce risks. One or two finalist will be selected to receive the program’s budget of $450 million (minus the cost of a launch vehicle and mission operations) and will launch in 2020 at the earliest.
Artist's concept of the VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) spacecraft, a proposed mission for NASA's Discovery Program that would launch by the end of 2021. Credit: NASA/JPL-Caltech
In February of 2014, NASA’s Discovery Program asked for proposals for the their 13th mission. Last week, five semifinalist were selected from the original 27 submissions for further investigation and refinement. Of the possible missions that could be going up, two involve sending a robotic spacecraft to a planet that NASA has not been to in decades: Venus!
The first is the DAVINCI spacecraft, which would study the chemical composition of Venus’ atmosphere. Meanwhile, the proposed VERITAS mission – or The Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy spacecraft – would investigate the planet’s surface to determine just how much it has in common with Earth, and whether or not it was ever habitable.
In many respects, this mission would pick up where Magellan left off in the early 1990s. Having reached Venus in 1990, the Magellan spacecraft (otherwise known as the Venus Radar Mapper) mapped nearly the entire surface with an S-band Synthetic Aperture Radar (SAR) and microwave radiometer. From the data obtained, NASA scientists were able to make radar altimeter measurements of the planet’s topography.
Deployment of the Magellan spacecraft with the Inertial Upper Stage (IUS) booster during the STS 30 Atlantis flight. Credit: NASA
These measurements revolutionized our understanding of Venus’ geology and the geophysical processes that have shaped the planet’s surface. In addition to revealing a young surface with few impact craters, Magellan also showed evidence of volcanic activity and signs of plate tectonics.
However, the lack of finer resolution imagery and topography of the surface hampered efforts to answer definitively what role these forces have played in the formation and evolution of the surface. As a result, scientists have remained unclear as to what extent certain forces have shaped (and continue to shape) the surface of Venus.
With a suite of modern instruments, the VERITAS spacecraft would produce global, high-resolution topography and imaging of Venus’ surface and produce the first maps of deformation and global surface composition. These include an X-band radar configured as a single pass radar interferometer (known as VISAR) which would be coupled with a multispectral NIR emissivity mapping capability.
Three-dimensional simulation of Gula Mons captured by the Magellan Synthetic Aperture Radar (SAR) combined with radar altimetry. Credit: NASA/JPL
Using these, the VERITAS probe will be able to see through Venus’ thick clouds, map the surface at higher resolution than Magellan, and attempt to accomplish three major scientific goals: get a better understanding of Venus’ geologic evolution; determine what geologic processes are currently operating on Venus (including whether or not active volcanoes still exist); and find evidence for past or present water.
Suzanne Smrekar of NASA’s Jet Propulsion Laboratory (JPL) is the mission’s principal investigator, while the JPL would be responsible for managing the project. As she explained to Universe Today via email:
“VERITAS’ objectives are to reveal Venus’ geologic history, determine how active it is, and search for the fingerprints of past and present water. The overarching question is ‘How Earthlike is Venus?’ As more and more exoplanets are discovered, this information is essential to predicting whether Earth-sized planets are more likely to resemble Earth or Venus.”
Venus, as imaged by the Magellan spacecraft using Synthetic Aperture Radar (SAR). Credit: NASA/JPL
In many ways, VERITAS and DAVINCI represent a vindication for Venus scientists in the United States, who have not sent a probe to the planet since the Magellan orbiter mission ended in 1994. Since that time, efforts have been largely focused on Mars, where orbiters and landers have been looking for evidence of past and present water, and trying to piece together what Mars’ atmosphere used to look like.
But with Discovery Mission 13 and its five semi-finalists, the focus has now shifted onto Venus, near-Earth objects, and a variety of asteroids. As John Grunsfeld, astronaut and associate administrator for NASA’s Science Mission Directorate in Washington, explained:
“The selected investigations have the potential to reveal much about the formation of our solar system and its dynamic processes. Dynamic and exciting missions like these hold promise to unravel the mysteries of our solar system and inspire future generations of explorers. It’s an incredible time for science, and NASA is leading the way.”
Each investigation team will receive $3 million to conduct concept design studies and analyses. After a detailed review and evaluation of the concept studies, NASA will make the final selections by September 2016 for continued development. This final mission (or missions) that are selected will launcd by 2020 at the earliest.
The sky sparkles with the Moon (top, overexposed), Regulus, Venus, Mars, and Jupiter at dawn this morning October 7, 2015.
Tomorrow morning might be a good time to call for extra celestial traffic control. A slip of a crescent Moon will join a passel of planets in the dawn sky for the first of several exciting conjunctions over the next few days.
The scene facing east about 1 1/2 hours before sunrise Thursday morning Oct. 8. Let your eyes delight in the tumble of Moon and planets. Source: Stellarium
In the space of three mornings beginning tomorrow, four planets, the Moon and the star Regulus will participate in six separate conjunctions. Here’s how it’ll play out. Time are shown in UT / Greenwich Mean Time and Central Daylight and 1° equals two full moon diameters:
October 8: Venus 2.5° south of Regulus at 18 UT (1 p.m. CDT)
October 8: Regulus 3.1° north of the moon at 19 UT (2 p.m. CDT)
October 8: Venus 0.6° north of the moon at 20 UT (3 p.m. CDT)
October 9: Mars 3.2° north of the moon at 14 UT (9 a.m. CDT)
October 9: Jupiter 2.5° north of the moon at 21 UT (4 p.m.)
October 11: Mercury 0.8° north of the moon 11 UT (6 a.m. CDT)
The crescent Moon will be near Venus all day Thursday for the Americas until it sets in late afternoon. What a great opportunity to catch sight of the planet in the middle of the day. This binocular view depicts their arrangement around noon CDT Oct. 8, when the planet lies less than 2° from the Moon. Source:: Stellarium
Since several of the events occur in the middle of the afternoon for skywatchers in the Americas, here’s an expanded viewing guide:
* Thursday, October 8: Skywatchers will see Venus pass 2.5° south of Leo’s brightest star Regulus with a cool crescent moon a little more than 3° to the west of the brilliant planet. If you live in Japan and the Far East, you’ll see a splendidly close conjunction of the moon and Venus at dawn on October 9, when the pair will be separated by a hair more than one moon diameter (0.6°). At nearly the same time, the moon will be in conjunction with Regulus.
Observers in Australia and New Zealand will see the Moon occult Venus in a dark sky sky before dawn (or in daylight, depending on exact location) on the 9th. Click HERE for information, times and a map for the event.
Ready to set the alarm again? The following morning, October 9, the moon makes a neat triangle with Jupiter and Mars. Source: Stellarium
* Friday, October 9: An even thinner moon passes about 3° north of Mars in the Americas at dawn and approximately 4° from Jupiter. Watch for the three luminaries to sketch a nifty triangle in the eastern sky 90 minutes to an hour before sunrise. Venus will gaze down at the planetary conclave 10° further west.
There’s not much of the Moon left by Saturday morning the 11th. The knife-edge crescent will hang less than a degree below the planet Mercury 40 minutes before sunrise. Make sure you find a spot with a good eastern horizon. Source: Stellarium
* Sunday, October 11: Mercury, which has quietly taken up residence again in the dawn sky, hovers 0.8° above a hair-thin moon this morning at 6 a.m. CDT. Best views will be about 45 minutes before sunrise, when the pair rises high enough to clear distant trees. Bring binoculars to help you spot the planet.
After a short break, Mars and Jupiter will cozy up 0.4 degree apart just before the start of dawn on October 17 CDT. Venus won’t be far away. Source: Stellarium
You’re thinking, why does this all have to happen in the morning? Thankfully, sunrise occurs around 7 a.m. for many locations, so you can see all these cool happenings in twilight around 6 a.m. — not terribly unreasonable. And now that the The Martian has finally hit the movie theaters, what better time to see the planet in the flesh? By pure coincidence, the location of stranded astronaut Mark Watney in the fictional account — Acidalia Planitia (Mare Acidalium) — will be facing dawn risers across the Americas and Hawaii this week.
October wraps up with a tight trio of three planets before dawn. It will be the closest gathering of three planets since May 27, 2013. The next won’t happen till January 10, 2021. Source: Stellarium
Dare I say this string of continuous conjunctions is only a warm-up for more to come? Earth’s revolution around the Sun quickly brings Jupiter higher in the eastern sky, while Mars races eastward as if on a collision course. The following Saturday on October 17, the two will meet in conjunction less than 1/2 degree (one Full Moon width) apart. Very nice!
But it gets even better. On Tuesday morning, October 27, you’ll see all three planets huddle at dawn. One degree will separate Jupiter and Venus with Mars bringing up the rear several degrees further east. Feast on the view because there won’t be a more compact arrangement of three planets again until January 10, 2021.
Itching for some cometary action? After a fine winter’s performance from Comet C/2014 Q2 Lovejoy, 2015 has seen a dearth of good northern hemisphere comets. That’s about to change, however, as Comet C/2013 US10 Catalina joins the planetary lineup currently gracing the dawn sky in early November. Currently located in the constellation Centaurus and shining at magnitude +6, Comet US10 Catalina has already put on a fine show for southern hemisphere observers over the last few months during Act I.
Currently buried in the dusk sky, Comet US10 Catalina is bashful right now, as it shares nearly the same right ascension with the Sun over the next few weeks, passing just eight degrees from our nearest star as seen from our Earthly vantage point on November 7th — and perhaps passing juuusst inside of the field of view for SOHO’s LASCO C3 camera — and into the dawn sky.
The altitude of Comet US10 Catalina in November and December at dawn as seen from latitude 30 degrees north. Image credit: Starry Night Education software.
The hunt is on come early November, as Comet US 10 Catalina vaults into the dawn sky. From 30 degrees north latitude here in Central Florida, the comet breaks 10 degrees elevation an hour prior to local sunrise right around November 20th. This should see the comet peaking in brightness right around magnitude +5 near perihelion the same week on November 16th.
The projected light curve of Comet US10 Catalina, with observations thus far (black dots) Image credit: Adapted from Seiichi Yoshida’s Weekly Information About Bright Comets
The angle of the comet’s orbit is favorable for northern hemisphere viewers in mid-November, as viewers start getting good looks in the early morning from latitude 30 degrees northward and the comet gains about a degree of elevation per day. This will bring it up out of the murk of twilight and into binocular view.
Mark your calendar for the morning of December 7th, as the crescent Moon, Venus and a (hopefully!) +5 magnitude comet US10 Catalina will all fit within a five degree circle.
The view on the morning of December 7th. Image credit: Starry Night Education software
Here are some key dates with celestial destiny for Comet US10 Catalina for the remainder of 2015:
October
20-Crosses into the constellation Hydra.
November
2-Crosses into the constellation Libra.
16-Crosses into the constellation Virgo.
16-Reaches perihelion at 0.823 AU (127.6 million kilometers) from Sun.
26-Crosses the ecliptic plane northward.
27-Passes less than one degree from the +4.5 magnitude star Lambda Virginis.
The celestial path of Comet US 10 Catalina through the end of 2015. Image Credit: Starry Night Education software
December
7-Fits inside a five degree circle with Venus and the waning crescent Moon.
8-Passes less than one degree from the +4 magnitude star Syrma (Iota Virginis).
17-Crosses the celestial equator northward.
24-Crosses into the constellation Boötes.
In January, Comet US10 Catalina starts the New Year passing less than a degree from the -0.05 magnitude star Arcturus. From there, the comet may drop below +6 magnitude and naked eye visibility by mid-month, just prior to its closest approach to the Earth at 0.725 AU (112.3 million kilometers) on January 17th. By February 1st, the comet may drop below +10th magnitude and binocular visibility, into the sole visual domain of large light bucket telescopes under dark skies.
Comet US10 Catalina imaged from Australia on July 21st, 2015. Image credit: Alan Tough
Or not. Comets and predictions of comet brightness are always notoriously fickle, and rely mainly on just how the comet performs near perihelion. Then there’s twilight extinction to contend with, and the fact that the precious magnitude of the comet is diffused over its extended surface area, often causing the comet to appear fainter visually than the quoted magnitude.
But do not despair. Comets frequently under-perform pre-perihelion passage, only to put on brilliant shows after. Astronomers discovered Comet US10 Catalina on Halloween 2013 from the Catalina Sky Survey based just outside of Tucson, Arizona. On a several million year orbit, all indications are that Comet US10 Catalina is a dynamically new Oort Cloud visitor and will probably get ejected from the solar system after this all-too brief fling with the Sun. Its max velocity at perihelion will be 46.4 kilometers per second, three times faster than the New Horizons spacecraft currently on an escape trajectory out of the solar system.
The odd ‘US10’ designation comes from the comet’s initial identification as an asteroidal object, later upgraded to cometary status. The comet’s high orbital inclination of 149 degrees assured two separate showings, as the comet approached the Sun as seen from the Earth’s southern hemisphere, only to then vault up over the northern hemisphere post-perihelion. As is often the case, the comet was closest to the Sun at exactly the wrong time: had perihelion occurred around May, the comet would’ve passed the Earth just 0.17 AU (15.8 million miles or 26.3 million kilometers) distant! That might’ve placed the comet in the negative magnitudes and perhaps earned it the title of ‘the Great Comet of 2015…’
The orbit of Comet US10 Catalina and the view during closest Earth approach. Image credit: NASA/JPL
But such was not to be.
Ah, but the next ‘big one’ could come at any time. In 2016, we’re tracking comet C/2013 X1 PanSTARRS, which will ‘perhaps’ become a fine binocular comet next summer…
More to come. Perhaps we’ll draft up an Act III for US10 Catalina in early January if it’s a top performer.
NASA's James Webb Telescope, shown in this artist's conception, will provide more information about previously detected exoplanets. Beyond 2020, many more next-generation space telescopes are expected to build on what it discovers. Credit: NASA
Researchers at the University of Washington’s Virtual Planetary Laboratory have devised a new habitability index for judging how suitable alien planets might be for life, and the top prospects on their list are an Earthlike world called Kepler-442b and a yet-to-be confirmed planet known as KOI 3456.02.
Those worlds both score higher than our own planet on the index: 0.955 for KOI 3456.02 and 0.836 for Kepler-442b, compared with 0.829 for Earth and 0.422 for Mars. The point of the exercise is to help scientists prioritize future targets for close-ups from NASA’s yet-to-be-launched James Webb Space Telescope and other instruments.
Astronomers have detected more than 1,000 confirmed planets and almost 5,000 candidates beyond our solar system, with most of them found by NASA’s Kepler Space Telescope. More than 100 of those have been characterized as potentially habitable, and hundreds more are thought to be waiting in the wings. The Webb telescope is expected to start taking a closer look soon after its scheduled launch in 2018.
“Basically, we’ve devised a way to take all the observational data that are available and develop a prioritization scheme,” UW astronomer Rory Barnes said Monday in a news release, “so that as we move into a time when there are hundreds of targets available, we might be able to say, ‘OK, that’s the one we want to start with.'”
This isn’t the first habitability index to be devised. Traditionally, astronomers focus on how close a particular exoplanet’s mass is to Earth’s, and whether its orbit is in a “Goldilocks zone” where water could exist in liquid form. But in a paper accepted for publication in the Astrophysical Journal, Barnes and his colleagues say their scheme includes other factors such as a planet’s estimated rockiness and the eccentricity of its orbit.
The formula could be tweaked even further in the future. “The power of the habitability index will grow as we learn more about exoplanets from both observations and theory,” said study co-author Victoria Meadows.
NASA's latest round of Discovery Program missions. Credit: NASA
It’s no secret that there has been a resurgence in interest in space exploration in recent years. Much of the credit for this goes to NASA’s ongoing exploration efforts on Mars, which in the past few years have revealed things like organic molecules on the surface, evidence of flowing water, and that the planet once had a denser atmosphere – all of which indicate that the planet may have once been hospitable to life.
But when it comes to the future, NASA is looking beyond Mars to consider missions that will send missions to Venus, near-Earth objects, and a variety of asteroids. With an eye to Venus, they are busy investigating the possibility of sending the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) spacecraft to the planet by the 2020s.
Led by Lori Glaze of the Goddard Spaceflight Center, the DAVINCI descent craft would essentially pick up where the American and Soviet space programs left off with the Pioneer and Venera Programs in the 1970s and 80s. The last time either country sent a probe into Venus’ atmosphere was in 1985, when the Soviet probes Vega 1 and 2 both orbited the planet and released a balloon-supported aerobot into the upper atmosphere.
Model of the Vega 1 probe and landing apparatus at the Udvar-Hazy Center, Dulles International Airport, Chantilly, Virginia. Credit: historicspacecraft.com
These probes both remained operational for 46 hours and discovered just how turbulent and powerful Venus’ atmosphere was. In contrast, the DAVINCI probe’s mission will be to study both the atmosphere and surface of Venus, and hopefully shed some light on some of the planet’s newfound mysteries. According to the NASA release:
“DAVINCI would study the chemical composition of Venus’ atmosphere during a 63-minute descent. It would answer scientific questions that have been considered high priorities for many years, such as whether there are volcanoes active today on the surface of Venus and how the surface interacts with the atmosphere of the planet.”
These studies will attempt to build upon the data obtained by the Venus Express spacecraft, which in 2008/2009 noted the presence of several infrared hot spots in the Ganis Chasma region near the the shield volcano of Maat Mons (shown below). Believed to be due to volcanic eruptions, this activity was thought to be responsible for significant changes that were noted in the sulfur dioxide (SO²) content in the atmosphere at the time.
What’s more, the Pioneer Venus spacecraft – which studied the planet’s atmosphere from 1978 until its orbit decayed in 1992 – noted a tenfold decreased in the density of SO² at the cloud tops, which was interpreted as a decline following an episode of volcanogenic upwelling from the lower atmosphere.
3-D perspective of the Venusian volcano, Maat Mons, generated from radar data from NASA’s Magellan mission. Credit: NASA/JPL
Commonly associated with volcanic activity here on Earth, SO² is a million times more abundant in Venus’ atmosphere, where it helps to power the runaway greenhouse effect that makes the planet so inhospitable. However, any SO² released into Venus’ atmosphere is also short-lived, being broken down by sunlight within a matter of days.
Hence, any significant changes in SO² levels in the upper atmosphere must have been a recent addition, and some scientists believe that the spike observed in 2008/2009 was due to a large volcano (or several) erupting. Determining whether or not this is the case, and whether or not volcanic activity plays an active role in the composition of Venus’s thick atmosphere, will be central to DAVINCI’s mission.
Along with four other mission concepts, DAVINCI was selected as a semifinalist for the NASA Discovery Program‘s latest calls for proposed missions. Every few years, the Discovery Program – a low-cost planetary missions program that is managed by the JPL’s Planetary Science Division – puts out a call for missions with an established budget of around $500 million (not counting the cost of launch or operation).
The latest call for submissions took place in February 2014, as part of the Discovery Mission 13. At the time, a total of 27 teams threw their hats into the ring to become part of the next round of space exploration missions. Last Wednesday, September 30th, 2015, five semifinalists were announced, one (or possibly two) of which will be chosen as the winner(s) by September 2016.
Artist rendition of NASA’s Mars InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) Lander, which was selected as part of the Discovery Programs 2010 call for submissions and will be launched by 2016. Credit: JPL/NASA
These finalists will receive $3 million in federal grants for detailed concept studies, and the mission (or missions) that are ultimately chosen will be launched by December 31st, 2021. The Discovery Program began back in 1992, and launched its first mission- the Mars Pathfinder – in 1996. Other Discovery missions include the NEAR Shoemaker probe that first orbited an asteroid, and the Stardust-NExT project, which returned samples of comet and interstellar dust to Earth.
NASA’s MESSENGER spacecraft, the planet-hunting Kepler telescope, and the Dawn spacecraft were also developed and launched under the Discovery program. The winning proposal of the Discovery Program’s 12th mission, which was issued back in 2010, was the InSight Mars lander. Set to launch in March of 2016, the lander will touch down on the red planet, deploy instruments to the planet’s interior, and measure its seismic activity.
NASA hopes to infuse the next mission with new technologies, offering up government-furnished equipment with incentives to sweeten the deal for each proposal. These include a supply of deep space optical communications system that are intended to test new high-speed data links with Earth. Science teams that choose to incorporate the laser telecom unit will be entitled to an extra $30 million above their $450 million cost cap.
If science teams wish to send entry probes into the atmospheres of Venus or Saturn, they will need a new type of heat shield. Hence, NASA’s solicitation includes a provision to furnish a newly-developed 3D-woven heat shield with a $10 million incentive. A deep space atomic clock is also available with a $5 million bonus, and NASA has offered to provide xenon ion thrusters and radioisotope heater units without incentives.
As with previous Discovery missions, NASA has stipulated that the mission must use solar power, limiting mission possibilities beyond Jupiter and Saturn. Other technologies may include the NEXT ion thruster and/or re-entry technology.
The September 17, 2015 total lunar eclipse - the last of the recent tetrad of lunar eclipses over the past 17 months - was darker than expected. Several factors described below were in play. This photo was taken in Washington's Olympic National Park. Credit: Rick Klawitter
First off, a huge thank you to everyone who made and sent their Danjon scale estimate of the totally-eclipsed Moon’s brightness to Dr. Richard Keen, University of Colorado atmospheric scientist. Your data were crucial to his study of how aerosols in Earth’s atmosphere and other factors influence the Moon’s appearance.
Grateful for your help, Keen received a total of 28 observations from 7 different countries.
Graph created by Dr. Richard Keen plotting Danjon L values submitted by Universe Today readers and others that compare predicted values (top curve) with observed values. The Moon was about half as bright during totality as expected with L=1.9. Credit: Dr. Richard A. Keen
Using the Danjon information and estimates of the Moon’s brightness using the reverse binocular method, Keen crunched the data and concluded that the Moon was about 0.6 L (Danjon) units darker than expected and 0.4 magnitude dimmer, a brightness reduction of 33%. This agrees well with my own observation and possibly yours, too. No wonder so many stars sparkled near the Moon that night.
Lunar eclipse brightness is rated on the Danjon scale where “0” equals a dark gray totality and “4” a bright, coppery yellow. Credit: Bob King
I think it’s safe to say, most of us expected a normal or even bright totality. So why was it dark? Several factors were at play — one to do with the Moon’s location in Earth’s shadow, the other with a volcanic eruption and a third with long-term, manmade pollution.
During a perigean eclipse, the Moon passes more deeply into Earth’s shadow compared to one that happens near apogee, when the moon is most distant from Earth. Moon distances not to scale and for illustration only. Credit: Bob King
You’ll recall that the eclipse occurred during lunar perigee, when the Moon swings closest to Earth in its 27-day orbit. Being closer, it also tracked deeper into Earth’s umbra or inner shadow which narrows the farther back of the planet it goes. An apogean Moon (farthest from Earth) passes through a more tapered cone of darkness closer to the penumbra, where sunlight mixes with shadow. A Moon nearer Earth would find the umbral shadow roomier with the light-leaking penumbra further off in the distance.
On April 24, 2015, NASA’s Terra satellite acquired this photo of the ash and gas plume from Calbuco volcano in southern Chile. Credit: NASA
But there’s more. Working independently, Steve Albersof NOAA and Brazilian astronomer Helio Vital suggested another reason: aerosols in the atmosphere. “Earth’s stratosphere is no longer completely clean of volcanic ashes,” said Vital in an e-mail communication. “In fact, lingering aerosols (ash, dust, sulfuric acid droplets) from the explosion of Calbuco five months ago may be to blame for that excessive darkening.”
With the lunar horizon in the foreground, the Earth passes in front of the Sun on September 27, 2015 in this simulation, revealing the red ring of sunrises and sunsets along the limb of the planet responsible for illuminating the Moon during the eclipse. The clarity of the stratosphere at eclipse time can greatly affect lunar brightness during totality. The Earth and Sun are in Virgo for observers on the Moon with the bright star Beta Virginis at top. Click to see the video. Credit: NASA’s Scientific Visualization Studio
While much of the debris blasted into the stratosphere made for colorful sunsets in the southern hemisphere, some of that material has likely made its way to the northern hemisphere. Albers has noticed an increase in yellow and purple sunsets in his home town of Boulder in recent months, telltale signs of volcanic spew at play.
Forest fires that raged across the western states and Canadian provinces all spring and summer may also have contributed. Most of that smoke usually stays in the lower part of the atmosphere, but some may have found its way to the stratosphere, the very layer responsible for transmitting most of the sunlight that falls into Earth’s shadow and colors the moon.
Graph showing magnitude estimates of the Moon’s brightness during totality using the reverse binocular method. The predicted magnitude was -1.7 (a little brighter than Sirius) vs. the observed -1.3. Credit: Dr. Richard A. Keen
Sunlight has to pass through these light-absorbing minerals and chemicals on its way through the atmosphere and into Earth’s shadow. Less light means a darker moon during total eclipse. Coincidentally, much of the totally eclipsed Moon passed through the southern half of the umbra which “increased the effectiveness of the Calbuco aerosols (which are still more concentrated in the southern hemisphere than the northern) at dimming the light within the umbra,” writes Keen.
Oceanus Procellarum and Mare Imbrium are large, dark volcanic plains that contributed to the Moon’s faintness and dark-hued totality. Credit: Bob King
It also so happened that the darkest part of the moon coincided with two vast, dark volcanic plains called Oceanus Procellarum (Ocean of Storms) and Mare Imbrium, artificially enhancing the overall gloom over the northern half of the Moon.
U.S. satellite-derived map of PM2.5 (fine particulate matter which includes sulfates and soot) averaged over 2001-2006. Credit: Dalhousie University, Aaron van Donkelaar
Finally, the human hand may also have played a role in lunar color and brightness. The burning of coal and oil has caused a gradual increase in the amount of human-made sulfate aerosols in the atmosphere since the start of the industrial revolution. According to NASA, at current production levels, human-made sulfate aerosols are believed to outweigh the naturally produced sulfate aerosols. No surprise that the concentration of aerosols is highest in the northern hemisphere where most industrial activity is found.
Isn’t it fascinating that one blood-red Moon can tell us so much about the air we breathe? Thank you again for your participation!
Titan's dense, hydrocarbon rich atmosphere remains a focal point of scientific research. Credit: NASA
In ancient Greek lore, the Titans were giant deities of incredible strength who ruled during the legendary Golden Age and gave birth to the Olympian gods we all know and love. Saturn‘s largest moon, known as Titan, is therefore appropriately named. In addition to being Saturn’s largest moon – and the second-largest moon in the Solar System (after Jupiter’s moon Ganymede) – it is larger by volume than even the smallest planet, Mercury.
Beyond its size, Titan is also fascinating because it is the only natural satellite known to have a dense atmosphere, a fact which has made it very difficult to study until recently. On top of all that, it is the only object other than Earth where clear evidence of stable bodies of surface liquid has been found. All of this makes Titan the focal point of a great deal of curiosity, and a prime location for future scientific missions.
Discovery and Naming:
Titan was discovered on March 25th, 1655, by the Dutch astronomer Christiaan Huygens. Huygens had been inspired by Galileo’s improvements in telescopes and his discovery of moons circling Jupiter in 1610. By 1650, he went about developing a telescope of his own with the help of his brother (Constantijn Huygens, Jr.) and observed the first moon of Saturn.
In 1655, Huygens named it Saturni Luna (Latin for “Saturn’s moon”) in a tract De Saturni Luna Observatio Nova (“A New Observation of Saturn’s Moon”). As Giovanni Domenico Cassini discoveries four more moons around Saturn between 1673 and 1686, astronomers began to refer to them as Saturn I through V (with Titan being in the fourth position as Saturn IV).
A replica of the telescope which William Herschel used to observe Uranus. Credit: Alun Salt/Wikimedia Commons
After William Herschel’s discovery of Mimas and Enceladus in 1789, which are closer to Saturn than any of the larger moons, Saturn’s moons once again had to be re-designated. Thenceforth, Titan status became fixed as Saturn VI, despite the discovery of several smaller moons that were closer to Saturn since then.
The name Titan, along with the names for all the seven major satellites of Saturn, were suggested by William Herschel’s son, John. In 1847, John Herschel published Results of Astronomical Observations Made at the Cape of Good Hope, in which he suggested that the moons be named after the mythological Titans – the brothers and sisters of Cronus, who is the Greek equivalent to Saturn.
In 1907, Spanish astronomer Josep Comas i Solà observed limb darkening of Titan. This effect, where the center part of a planet or star appears brighter than the edge (or limb), was the first indication that Titan had an atmosphere. In 1944, Gerard P. Kuiper used a spectroscopic technique to determine that Titan had an atmosphere composed of methane.
Size. Mass and Orbit:
With a mean radius of 2576 ± 2 km and a mass of 1.345 × 1023 kg, Titan is 0.404 the size of Earth (or 1.480 Moons) and 0.0225 times as massive (1.829 Moons). Its orbit has a minor eccentricity of 0.0288, and its orbital plane is inclined 0.348 degrees relative to Saturn’s equator. It’s average distance from Saturn (semi-major axis) is 1,221,870 km – ranging from 1,186,680 km at periapsis (closest) to 1,257,060 km at apoapsis (farthest).
Diameter comparison of Titan, the Moon, and Earth. Credit: NASA/JPL/Space Science Institute/Gregory H. Revera
Titan takes 15 days and 22 hours to complete a single orbit of Saturn. Like the Moon and many satellites that orbit the other gas giants, its rotational period is identical to its orbital period. Thus, Titan is tidally-locked and in a synchronous rotation with Saturn, which means one face is permanently pointed towards the planet.
Composition and Surface Features:
Though similar in composition to Dione and Enceladus, Titan is denser due to gravitational compression. In terms of diameter and mass (and hence density) Titan is more similar to the Jovian moons of Ganymede and Callisto. Based on its bulk density of 1.88 g/cm3, Titan’s composition is believed to consist half of water ice and half of rocky material.
It’s internal makeup is likely differentiated into several layers, with a 3,400-kilometre (2,100 mi) rocky center surrounded by layers composed of different forms of crystalized ice. Based on evidence provided by the Cassini-Huygens mission in 2005, it is believed that Titan may also have a subsurface ocean which exists between the crust and several deeper layers of high-pressure ice.
This subsurface ocean is believed to be made up of water and ammonia, which allows the water to remain in a liquid state even at temperatures as low as 176 K (-97 °C). Evidence of a systematic shift of the moon’s surface features (which took place between October 2005 and May 2007) suggests that the crust is decoupled from the interior – possibly by a liquid layer in between – as well as the way the gravity field varies as Titan orbits Saturn.
Diagram of the internal structure of Titan according to the fully differentiated dense-ocean model. Credit: Wikipedia Commons/Kelvinsong
The surface of Titan is relatively young – between 100 million and 1 billion years old – despite having been formed during the early Solar System. In addition, it appears to be relatively smooth, with impact craters having been filled in. Height variation is also low, ranging by little more than 150 meters, but with the occasional mountain reaching between 500 meters and 1 km in height.
This is believed to due to geological processes which have reshaped Titan’s surface over time. For example, a range measuring 150 km (93 mi) long, 30 km (19 mi) wide, and 1.5 km (0.93 mi) tall has been potted in the southern hemisphere, composed of icy material and covered in methane snow. The movement of tectonic plates, perhaps influenced by a nearby impact basin, could have opened a gap through which the mountain’s material upwelled.
Then there is Sotra Patera, a chain of mountains that is 1000 to 1500 m (0.62 and 0.93 mi) in height, has some peaks topped by craters, and what appears to be frozen lava flows at its base. If volcanism on Titan really exists, the hypothesis is that it is driven by energy released from the decay of radioactive elements within the mantle, tidal flexing caused by Saturn’s influence, or possibly the interaction of Titan’s subsurface ice layers.
An alternate theory is that Titan is a geologically dead world and that the surface is shaped by a combination of impact cratering, flowing-liquid and wind-driven erosion, mass wasting and other externally-motivated processes. According to this hypothesis, methane is not emitted by volcanoes but slowly diffuses out of Titan’s cold and stiff interior.
Updated maps of Titan, based on the Cassini imaging science subsystem. Credit: NASA/JPL/Space Science Institute
The few impact craters discovered on Titan’s surface include a 440 km (270 mi) wide two-ring impact basin named Menrva, which is identifiable from its bright-dark concentric pattern. A smaller, 60 km (37 mi) wide, flat-floored crater named Sinlap and a 30 km (19 mi) crater with a central peak and dark floor named Ksa have also been observed.
Radar and orbital imaging has also revealed a number of “crateriforms” on the surface, circular features that may be impact related. These include a 90 km (56 mi) wide ring of bright, rough material known as Guabonito, which is thought to be an impact crater filled in by dark, windblown sediment. Several other similar features have been observed in the dark Shangri-la and Aaru regions.
The presence of cryovolcanism has also been theorized based on the fact that there is apparently not enough liquid methane on Titan’s surface (see below) to account for the atmospheric methane. However, to date, the only indications of cryovolcanism are particularly bright and dark features on the surface and 200 m (660 ft) structures resembling lava flows that were spotted in the region called Hotei Arcus.
Titan’s surface is also permeated by streaky features (aka. “sand dunes“), some of which are hundreds of kilometers in length and several meters high. These appear to be caused by powerful, alternating winds that are caused by the interaction of the Sun and Titan’s dense atmosphere. Titan’s surface is also marked by broad regions of bright and dark terrain.
Radar image of rows of dunes on Titan. Credit: NASA/JPL-Caltech
These include Xanadu, a large, reflective equatorial area that was first identified by the Hubble Space Telescope in 1994 and later by the Cassini spacecraft. This region (which is about the same size as Australia) is very diverse, being filled with hills, valleys, chasms and crisscrossed in places by dark lineaments – sinuous topographical features resembling ridges or crevices.
These could be an indication of tectonic activity, which would mean that Xanadu is geologically young. Alternatively, the lineaments may be liquid-formed channels, suggesting old terrain that has been cut through by stream systems. There are dark areas of similar size elsewhere on Titan, which have been revealed to be the patches of water ice and organic compounds that darkened due to exposure to UV radiation.
Methane Lakes:
Titan is also home to its famous “hydrocarbon seas”, lakes of liquid methane and other hydrocarbon compounds. Many of these have been spotted near the polar regions, such as Ontario Lacus. This confirmed methane lake near the south pole has a surface area of 15,000 km² (making it 20% smaller than its namesake, Lake Ontario) and a maximum depth of 7 meters (23 feet).
But the largest body of liquid is Kraken Mare, a methane lake near the north pole. With a surface area of about 400,000 km², it is larger than the Caspian Sea and is estimated to be 160 meters deep. Shallow capillary waves (aka. ripple waves) that are 1.5 centimeters high and moving at speeds of 0.7 meters per second have also been detected.
Mosaic of images taken in near infrared light showing Titan’s polar seas (left) and a radar image of Kraken Mare (right), both taken by the Cassini spacecraft. Credit: NASA/JPL
Then there is Ligeia Mare, the second largest known body of liquid on Titan, which is connected to Kraken Mare and also located near the north pole. With a surface area of about 126,000 km² and a shoreline that is over 2000 km (1240 mi) in length, it is larger than Lake Superior. Much like Kraken Mare, it takes its name from Greek mythology; in this case, after one of the sirens.
It was here that NASA first noticed a bright object measuring 260 km² (100 square miles), which they named “Magic Island”. This object was first spotted in July 2013, then disappeared later, only to reappear again (slightly changed) in August 2014 . It is believed to be inked to Titan’s changing seasons, and suggestions as to what it might be range from surface waves and rising bubbles to floating solids suspended beneath the surface.
Although most of the lakes are concentrated near the poles (where low levels of sunlight prevent evaporation), a number of hydrocarbon lakes have also been discovered in the equatorial desert regions. This includes one near the Huygens landing site in the Shangri-la region, which is about half the size of Utah’s Great Salt Lake. Like desert oases on Earth, it is speculated that these equatorial lakes are fed by underground aquifers.
Overall, the Cassini radar observations have shown that lakes cover only a few percent of the surface, making Titan much drier than Earth. However, the probe also provided strong indications that considerable liquid water exists 100 km below the surface. Further analysis of the data suggests that this ocean may be as salty as the Dead Sea.
During previous flybys, ‘Magic Island’ was not visible near Ligeia Mare’s coastline (left). Then, during Cassini’s July 20, 2013, flyby the feature appeared (right). Credit: NASA/JPL-Caltech/ASI/Cornell
Other studies suggest methane rainfall (see below) on Titan may interact with icy materials underground to produce ethane and propane that may eventually feed into rivers and lakes.
Atmosphere:
Titan is the only moon in the Solar System with a significant atmosphere, and the only body other than Earth who’s atmosphere is nitrogen-rich. Recent observations have shown that Titan’s atmosphere is denser than Earth’s, with a surface pressure of about 1.469 KPa – 1.45 times that of Earths. It is also about 1.19 times as massive as Earth’s atmosphere overall, or about 7.3 times more massive on a per-surface-area basis.
The atmosphere is made up of opaque haze layers and other sources that block most visible light from the Sun and obscure its surface features (similar to Venus). Titan’s lower gravity also means that its atmosphere is far more extended than Earth’s. In the stratosphere, the atmospheric composition is 98.4% nitrogen with the remaining 1.6% composed mostly of methane (1.4%) and hydrogen (0.1–0.2%).
There are trace amounts of other hydrocarbons, such as ethane, diacetylene, methylacetylene, acetylene and propane; as well as other gases such as cyanoacetylene, hydrogen cyanide, carbon dioxide, carbon monoxide, cyanogen, argon and helium. The hydrocarbons are thought to form in Titan’s upper atmosphere in reactions resulting from the breakup of methane by the Sun’s ultraviolet light, producing a thick orange smog.
Energy from the Sun should have converted all traces of methane in Titan’s atmosphere into more complex hydrocarbons within 50 million years—a short time compared to the age of the Solar System. This suggests that methane must be replenished by a reservoir on or within Titan itself. The ultimate origin of the methane in its atmosphere may be its interior, released via eruptions from cryovolcanoes.
False color image of Titan’s atmosphere. Credit: NASA/JPL/Space Science Institute/ESA
Titan’s surface temperature is about 94 K (-179.2 °C), which is due to the fact that Titan receives about 1% as much sunlight as Earth. At this temperature, water ice has an extremely low vapor pressure, so the little water vapor present appears limited to the stratosphere. The moon would be much colder, were it not for the fact that the atmospheric methane creates a greenhouse effect on Titan’s surface.
Conversely, haze in Titan’s atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, cancelling a portion of the greenhouse effect and making its surface significantly colder than its upper atmosphere. In addition, Titan’s atmosphere periodically rains liquid methane and other organic compounds onto its surface.
Based on studies simulating the atmosphere of Titan, NASA scientists have speculated that complex organic molecules could arise on Titan (see below). In addition, propene – aka. propylene, a class of hydrocarbon – has also been detected in Titan’s atmosphere. This is the first time propene has been found on any moon or planet other than Earth, and is thought to be formed from recombined radicals created by the UV photolysis of methane.
Habitability:
Titan is thought to be a prebiotic environment rich in complex organic chemistry with a possible subsurface liquid ocean serving as a biotic environment. Ongoing research of Titan’s atmosphere has led many scientists to theorize that conditions there are similar to what existed on a primordial Earth, with the important exception of a lack of water vapor.
Numerous experiments have shown that an atmosphere similar to that of Titan, with the addition of UV radiation, could give rise to complex molecules and polymer substances like tholins. In addition, independent research conducted by the University of Arizona reported that when energy was applied to a combination of gases like those found in Titan’s atmosphere, many organic compounds were produced. These includes the five nucleotide bases – the building blocks of DNA and RNA – as well as amino acids, which are the building blocks of protein.
Multiple laboratory simulations have been conducted that have led to the suggestion that enough organic material exists on Titan to start a chemical evolution process analogous to what is thought to have started life here on Earth. While this theory assumes the presence of water that would remain in a liquid state for longer periods that have been observed, organic life could theoretically survive in Titan’s hypothetical subsurface ocean.
Much like on Europa and other moons, this life would likely take the form of extremophiles – organisms that thrive in extreme environments. Heat transfer between the interior and upper layers would be critical in sustaining any subsurface oceanic life, most likely through hydrothermal vents located at the ocean-core boundary. That the atmospheric methane and nitrogen might be of biological origin has also been examined.
It has also been suggested that life could exist in Titan’s lakes of liquid methane, just as organisms on Earth live in water. Such organisms would inhale dihydrogen (H²) in place of oxygen gas (O²), metabolize it with acetylene instead of glucose, and then exhale methane instead of carbon dioxide. Although all living things on Earth use liquid water as a solvent, it is speculated that life on Titan could actually live in liquid hydrocarbons.
Several experiments and models have been constructed to test this hypothesis. For instance, atmospheric models have shown that molecular hydrogen is in greater abundance in the upper atmosphere and disappears near the surface – which is consistent with the possibility of methanogenic life-forms. Another study has shown that there are low levels of acetylene on Titan’s surface, which is also in line with the hypothesis of organisms consuming hydrocarbons.
In 2015, a team of chemical engineers at Cornell University went as far as to construct a hypothetical cell membrane that was capable of functioning in liquid methane under conditions similar to that on Titan. Composed of small molecules containing carbon, hydrogen, and nitrogen, this cell was said to have the same stability and flexibility as cell membranes on Earth. This hypothetical cell membrane was termed an “azotosome” (a combination of “azote”, French for nitrogen, and “liposome”).
However, NASA has gone on record as stating that these theories remain entirely hypothetical. Furthermore, it has been emphasized that other theories as to why hydrogen and acetylene levels are lower nearer to the surface are more plausible. These include a as-of-yet unidentified physical or chemical processes – such as a surface catalyst accepting hydrocarbons or hydrogen – or the existence of flaws in the current models of material flow.
Also, life on Titan would face tremendous obstacles compared to life on Earth – thus making any analogy to Earth problematic. For one, Titan is too far from the Sun, and its atmosphere lacks carbon monoxide (CO), which results in it not retaining enough heat or energy to trigger biological processes. Also, water only exists on Titan’s surface in solid form.
So while the prebiotic conditions that are associated with organic chemistry exist on Titan, life itself may not. However, the existence of these conditions remains a subject of fascination among scientists. And since its atmosphere is thought to be analogous to Earth’s in the distant past, researching Titan could help advance our understanding of the early history of the terrestrial biosphere.
Exploration:
Titan cannot be spotted without the help of instrumentation, and is often difficult for amateur astronomers because of interference from Saturn’s brilliant globe and ring system. And even after the development of high-powered telescopes, Titan’s dense, hazy, atmosphere made observations of the surface very difficult. Hence, observations of both Titan and its surface features prior to the space age were limited.
The first probe to visit the Saturnian system was Pioneer 11 in 1979, which took images of Titan and Saturn together and revealed that Titan was probably too cold to support life. Titan was examined in 1980 and 1981 by both the Voyager 1 and 2 space probes, respectively. While Voyager 2 managed to take snapshots of Titan on its way to Uranus and Neptune, only Voyager 1 managed to conduct a flyby and take pictures and readings.
This included readings on Titan’s density, composition, and temperature of the atmosphere, and obtain a precise measurement of Titan’s mass. Atmospheric haze prevented direct imaging of the surface; though in 2004, intensive digital processing of images taken through Voyager 1‘s orange filter did reveal hints of the light and dark features now known as Xanadu and Shangri-la.
Voyager 2 photograph of Titan, taken on Aug. 23rd, 1981, which shows some detail in the cloud systems on this Saturnian moon. Credit: NASA/JPL
Even so, much of the mystery surrounding Titan would not begin to be dispelled until the Cassini-Huygens mission – a joint project between NASA and the European Space Agency (ESA) named in honor of the astronomers who made the greatest discoveries involving Saturn’s moons. The spacecraft reached Saturn on July 1st, 2004, and began the process of mapping Titan’s surface by radar.
The Cassini probe flew by Titan on October 26th, 2004, and took the highest-resolution images ever of Titan’s surface, discerning patches of light and dark that were otherwise invisible to the human eye. Over the course of many close flybys of Titan, Cassini managed to detect abundant sources of liquid on the surface in the north polar region, in the form of many lakes and seas.
The Huygens probe landed on Titan on January 14th, 2005, making Titan the most distant body from Earth to have a space probe land on its surface. During the course of its investigations, it would discover that many of the surface features appear to have been formed by fluids at some point in the past.
After landing just off the easternmost tip of the bright region now called Adiri, the probe photographed pale hills with dark “rivers” running down to a dark plain. The current theory is that these hills (aka. “highlands”) are composed mainly of water ice, and that dark organic compounds – created in the upper atmosphere – may come down from Titan’s atmosphere with methane rain and become deposited on the plains over time.
Artist depiction of Huygens landing on Titan. Credit: ESA
Huygens also obtained photographs of a dark plain covered in small rocks and pebbles (composed of water ice) that showed evidence of erosion and/or fluvial activity. The surface is darker than originally expected, consisting of a mixture of water and hydrocarbon ice. The “soil” visible in the images is interpreted to be precipitation from the hydrocarbon haze above.
Several proposals for returning a robotic space probe to Titan have been made in recent years. These include the Titan Saturn System Mission (TSSM) – a joint NASA/ESA proposal for the exploration of Saturn’s moons – that envisions a hot-air balloon floating in Titan’s atmosphere and conducting research for a period of six months.
In 2009, it was announced that the TSSM lost out to a competing concept known the Europa Jupiter System Mission (EJSM) – a joint NASA/ESA mission that will consist of sending two probes to Europa and Ganymede to study their potential habitability.
There was also a proposal known as Titan Mare Explorer (TiME), a concept under consideration by NASA in conjunction with Lockheed Martin. This mission would involve a low-cost lander splashing down in a lake in Titan’s northern hemisphere and floating on the surface of the lake for 3 to 6 months. However, NASA announced in 2012 that it favored the lower-cost InSight Mars lander instead, which is scheduled to be sent to Mars in 2016.
Another mission to Titan was proposed in early 2012 by Jason Barnes, a scientist at the University of Idaho. Known as the Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR), this unmanned plane (or drone) would fly through Titan’s atmosphere and take high-definition images of the surface. NASA did not approve the requested $715 million at the time and the future of the project is uncertain.
Another lake lander project known as the Titan Lake In-situ Sampling Propelled Explorer (TALISE) was proposed in late 2012 by the Spanish-based private engineering firm SENER and the Centro de Astrobiología in Madrid. The major difference between this and the TiME probe is that the TALISE concept includes its own propulsion system, and would therefore not be limited to simply drifting on the lake when it splashes down.
In response to NASA’s 2010 Discovery Announcement, the concept known as Journey to Enceladus and Titan (JET) was proposed. Developed by Caltech and JPL, this mission would consist of a low-cost astrobiology orbiter that would be sent to the Saturnian system to asses the habitability potential of Enceladus and Titan.
In 2015, NASA’s Innovative Advanced Concepts (NIAC) awarded a Phase II grant to a proposed robotic submarine in order to further investigate and develop the concept. This submarine explorer, should it be deployed to Titan, will explore the depths of Kraken Mare to investigate its makeup and potential for supporting life.
Colonization:
The colonization of the Saturn system presents numerous advantages compared to other gas giants in the Solar System. According to Dr. Robert Zubrin – an American aerospace engineer, author, and an advocate for the exploration Mars – these include its relative proximity to Earth, its low radiation, and its excellent system of moons. Zubrin has also stated that Titan is the most important of these moons when it comes to building a base to develop the system’s resources.
Artist’s conception of possible Titan “floater” designed by NASA and the ESA. Credit: bisbos.com
For starters, Titan possess an abundance of all the elements necessary to support life, such as atmospheric nitrogen and methane, liquid methane, and liquid water and ammonia. Water could easily be used to generate breathable oxygen, and nitrogen is ideal as a buffer gas to create a pressurized, breathable atmosphere. In addition, nitrogen, methane and ammonia could all be used to produce fertilizer for growing food.
Additionally, Titan has an atmospheric pressure one and a half times that of Earth, which means that the interior air pressure of landing craft and habitats could be set equal or close to the exterior pressure. This would significantly reduce the difficulty and complexity of structural engineering for landing craft and habitats compared with low or zero pressure environments such as on the Moon, Mars, or the Asteroid Belt.
The thick atmosphere also makes radiation a non-issue, unlike with other planets or Jupiter’s moons. And while Titan’s atmosphere does contain flammable compounds, these only present a danger if they are mixed with sufficient enough oxygen – otherwise, combustion cannot be achieved or sustained. Finally, the very high ratio of atmospheric density to surface gravity also greatly reduces the wingspan needed for aircraft to maintain lift.
Beyond this, Titan presents many challenges for human colonization. For starters, the moon has a surface gravity of 0.138 g, which is slightly less than that of the Moon. Managing the long-term effects of this presents a challenge, and what those effects would be (especially for children born on Titan) are not currently known. However, they would likely include loss of bone density, muscle deterioration, and a weakened immune system.
Artist’s impression of future colonists flying over Ligeia Mare on Titan. Credit: Erik Wernquist/erikwernquist.com
The temperature on Titan is also considerably lower than on Earth, with an average temperature of 94 K (-179 °C, or -290.2 °F). Combined with the increased atmospheric pressure, temperatures vary very little over time and from one local to the next. Unlike in a vacuum, the high atmospheric density makes thermoinsulation a significant engineering problem. Nevetherless, compared to other cases for colonization, the problems associated with creating a human presence on Titan are relatively surmountable.
Titan is a moon that is shrouded in mystery, both literally and metaphorically. Until very recently, we were unable to discern what secrets it held because its atmosphere was simply too thick to see beneath. However, in recent years, we have managed to pull back that shroud and get a better look at the moon’s surface. But in many ways, doing this has only confounded the sense of mystery surrounding this world.
Perhaps someday we will send astronauts to Titan and find life forms there that completely alter our conception of what life is and where it can thrive. Perhaps we will find only extremophiles, life forms that live in the deepest parts of its interior ocean huddled around hydorthermal vents, since these spots are the only place on Titan where lifeforms can exist.
Perhaps we will even colonize Titan someday, and use it as a base for further exploration of the Solar System and resource extraction. Then, we may come to know the pleasures of looking up at a ringed planet in the sky while sailing on a methane lake, the hazy light of the Sun trickling down onto the cold, hydrocarbon seas. One can only hope… and dream!
We have many interesting articles about Titan here at Universe Today. Here are some on Titan’s atmosphere, it’s mysterious sand dunes, and how we might explore it with a robotic sailboat.
For more information on Titan’s methane lakes, check out this article on Titan’s north pole, and this one about Kraken Mare.
The new nova in Sagittarius is located just above the Spout in the Teapot and shines at about magnitude +9 this week - visible in a small telescope. Credit: Bob King
A nova farmer would do well in the fields of Sagittarius. Four nights ago on September 27, Japanese amateur Koichi Itagaki plucked another “new star” from its starry furrows, the third nova discovered there this year!
For a few days, it was informally called Nova Sagittarii #3, but today received the official title of V5669 Sagittarii. Like the others, this one’s bright enough to see in a small telescope.
Itagaki first recorded it in his patrol camera at magnitude +9.5. The universe conceals so many of its greatest conflagrations as points of light that go from faint to bright. Novae are no exception. Such is the amateur observer’s lot. We need bring a mental picture, knowledge and a bit of imagination to the table to appreciate this bits of light that go boom in the night.
Use this wide finder map of Sagittarius to get a general idea of the nova’s location. Lucky for us, it’s in the same low power field of view of the pretty cluster-dark nebula combo NGC 6520 and Barnard 86, the Inkspot Nebula. Source: Stellarium
Novae occur in binary star systems where a tiny but gravitationally-powerful white dwarf star pulls gases from a close companion star. The material piles up in a thin layer on the dwarf’s hot surface, fuses and burns explosively in a brilliant display of light. Suddenly, a star that may have been 15th or 20th magnitude flares brightly enough to see in a Walmart telescope.
Nova illustration with an expanding cloud of debris surrounding central fireball emitting red hydrogen-alpha light.
October’s not exactly prime time for viewing Sagittarius for mid-northern observers. By late evening twilight, it’s already in low in the southwestern sky. But if you can find an opening in that direction or if you’re lucky enough to have a 15-minute-wide gap between the trees like I do, you can spot this sucker. I set up my scope shortly before 8 o’clock or about an hour after sundown. Western Sagittarius remains in reasonably good view for about another hour.
Start at the Gamma Sagittarii and star hop from there to Gamma 1 and then north to the small star cluster NGC 6520 and adjacent dark nebula Barnard 86. You may not see the nebula because of atmospheric extinction at low altitude, but the cluster stands out well. A magnitude 7 star lies along its northwestern edge, and the nova is just 1/2 degree from there. If you have a go-to scope, its celestial coordinates are: R.A. 18 hours 3.5 minutes, Dec. -28 degrees 16 minutes.
AAVSO chart showing the location of V5669 Sgr. North is up. I’ve added the star cluster NGC 6520 and Barnard 86. To create your own customized charts of the nova, go to aavso.org, type in the star’s name and select “Create a finder chart”. Credit: American Assn. of Variable Star Observers (AAVSO)
To precisely pinpoint the nova, use the AAVSO chart, which also includes comparison stars with their magnitudes labeled (but without the decimal point). Do you notice any color? Photos show it as pale red from the emission of hydrogen-alpha light in the deep red of the visual spectrum. Novae often emit H-alpha especially in their early, hot “fireball” stage as gases are rapidly expanding from the explosion into space.
The pretty star cluster NGC 6520 and Ink Spot Nebula Barnard 86. The cross shows the location of the nova. The star field may look intimidating, but this time exposure photo reveals minions more than are visible in an amateur telescope. Credit: Johannes Schedler / panther-observatory.com
No telling what the star will do in the coming days. That’s what makes novae and variable stars in general so much fun to watch. I caught the star Monday night September 28 at magnitude +8.6. The following night it dropped to 9.3 and then edged back up to 9.2 last night. Astronomers study these fluctuations to understand a nova’s behavior and evolution. I can’t wait to see what it’s doing tonight.
One thing I really like about this nova is its location so near a pretty pair of deep sky objects. On your way to this amazing pinprick of light, stop by the cluster and dark nebula for a final farewell to the summer season.
Jupiter’s icy moon Europa. Credits: NASA/Jet Propulsion Laboratory, SETI Institute
Jupiter‘s four largest moons – aka. the Galilean Moons, consisting of Io, Europa, Ganymede, and Callisto – are nothing if not fascinating. Ever since their discovery over four centuries ago, these moons have been a source of many great discoveries. These include the possibility of internal oceans, the presence of atmospheres, volcanic activity, a magnetosphere (Ganymede), and the possibility of having more water than Earth.
But arguably, the most fascinating of the Galilean Moons is Europa: the sixth closest moon to Jupiter, the smallest of the four, and the sixth-largest moon in the Solar System. In addition to having an icy surface and a possible warm-water interior, this moon is considered to be one of the most likely places for finding life beyond Earth.
