What Are Comet Tails?

Comets are renowned for their big beautiful tails that stretch across the sky. But what’s in those things, anyway? And how can comets get multiple tails?

In the past, humans generally used one of two greetings for comets:
1. Dear God, what is that thing? Terrible omens! Surely we will all die in fire.
2. Dear God, what is that thing? Great omens! Surely we will all have a big party… where we all die in fire?

For example, the appearance of what came to be known as Halley’s comet in 1066 was seen as a bad omen for King Harold II. Conversely, it was a good omen for William the Conqueror.

Because of their tails and transitory nature, comets were long thought to be products of the Earth’s atmosphere. It wasn’t until the 1500s, when Tycho Brahe used parallax to determine a comet’s distance. He realized that they were Solar System objects, like planets.

So, good news, we no longer regard them as omens and everyone stopped panicking. Right? Wrong. When Comet Halley approached Earth in 1910, astronomers detected cyanide gas in its tail. French astronomer Camille Flammarion was quoted as saying the gas could “impregnate the atmosphere and possibly snuff out all life on the planet.” This caused a great deal of hysteria. Many bought gas masks and “comet pills” to protect themselves.

With the rise of photographic astronomy, it was found that comets often have two types of tails. A bright tail composed of ionized gas, and a dimmer one composed of dust particles. The ion tail always points away from the Sun. It’s actually being pushed away from the comet by the solar wind.

Comets often develop two tails as they near the sun - a curved dust tail and straight, ion tail. Credit: NASA
Comets often develop two tails as they near the sun – a curved dust tail and straight, ion tail. Credit: NASA

We now know that a comet’s ion tail contains “volatiles” such as water, methane, ammonia and carbon dioxide. These volatiles are frozen near the comet’s surface, and as they approach the Sun, they warm and become gaseous. This also causes dust on the comet’s surface to stream away. The heating of a comet by the Sun is not uniform.

Because of a comet’s irregular shape and rotation, some parts of the surface can be heated by sunlight, while other parts remain cold. In some cases this can mean that comets can have multiple tails, which creates amazing effects where different regions of a comet stream off volatiles.

Comet Lovejoy passing behind green oxygen and sodium airglow layers on December 22, 2011 seen from the space station. Credit: NASA/Dan Burbank
Comet Lovejoy passing behind green oxygen and sodium airglow layers on December 22, 2011 seen from the space station. Credit: NASA/Dan Burbank

These ion tails can be quite large, and some have been observed to be nearly 4 times the distance of the Earth from the Sun. And even though they fill a great volume, they are also pretty diffuse. If you condensed a comet’s tail down to the density of water, it wouldn’t even fill a swimming pool.

We also now know that there isn’t a clear dividing line between comets and asteroids. It’s not the case the comets are dirty snowballs and asteroids are dry rocks. There is a range of variation, and asteroids can gain dusty or gaseous tails and take on a comet-like appearance. In addition, we’ve also found comets orbiting other stars, known as exocomets.

And finally one last fact, the term comet comes from the Latin cometa, which indicated a hairy star.

So, what’s your favorite comet? Tell us in the comets below. And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

What’s Inside Jupiter?

Jupiter is like a jawbreaker. Dig down beneath the swirling clouds and you’ll pass through layer after layer of exotic forms of hydrogen. What’s down there, deep within Jupiter?

What’s inside Jupiter? Is it chameleons? Candy? Cake? Cheddar? Chemtrails? No one knows. No one can ever know.

Well, that’s not entirely true… or even remotely true. Jupiter is the largest planet in the Solar System and two and a half times the mass of the other planets combined. It’s a gas giant, like Saturn, Uranus, and Neptune. It’s almost 90% hydrogen and 10% helium, and then other trace materials, like methane, ammonia, water and some other stuff. What would be a gas on Earth behaves in very strange ways under Jupiter’s massive pressure and temperatures.

So what’s deep down inside Jupiter? What are the various layers and levels, and can I keep thinking of it like a jawbreaker? At the very center of Jupiter is its dense core. Astronomers aren’t sure if there’s a rocky region deep down inside. It’s actually possible that there’s twelve to forty five Earth masses of rocky material within the planet’s core. Now this could be rock, or hydrogen and helium under such enormous forces that it just acts that way. But you couldn’t stand on it. The temperatures are 35,000 degrees C. The pressures are incomprehensible.

Surrounding the core is a vast region made up of hydrogen. But it’s not a gas. The pressure and temperature transforms the hydrogen into an exotic form of liquid metallic hydrogen, similar to the liquid mercury you’d see in a thermometer. This metallic hydrogen region turns inside the planet, and acts like an electric dynamo. Similar to our planet’s own iron core, this gives the planet a powerful magnetic field.

The next level up is still liquid hydrogen, but the pressure’s lower, so it’s not metallic any more. And then above this is the planet’s atmosphere. The upper layers of Jupiter’s atmosphere is the only part we can see. Those bands on the planet are clouds of ammonia that rotate around the planet in alternating directions. The lighter color zones are colder ammonia ice upwelling from below. Here’s the exciting part. Astronomers aren’t sure what the darker regions are.

This animated gif shows Voyager 1's approach to Jupiter during a period of over 60 Jupiter days in 1979.  Credit: NASA.
This animated gif shows Voyager 1’s approach to Jupiter during a period of over 60 Jupiter days in 1979. Credit: NASA.

Still think you want to descend into Jupiter, to try and walk on its rocky interior? NASA tried that. In order to protect Jupiter’s moons from contamination, NASA decided to crash the Galileo spacecraft into the planet at the end of its mission. It only got point two percent of the way down through Jupiter’s radius before it was completely destroyed.

Jupiter is a remarkably different world from our own. With all that gravity, normally lightweight hydrogen behaves in completely exotic ways. Hopefully in the future we’ll learn more about this amazing planet we share our Solar System with.

What do you think? Is there a rocky core deep down inside Jupiter?

And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

A New Mantra: Follow the Methane — May Advance Search for Extraterrestrial Life

The search for life is largely limited to the search for water. We look for exoplanets at the correct distances from their stars for water to flow freely on their surfaces, and even scan radiofrequencies in the “water hole” between the 1,420 MHz emission line of neutral hydrogen and the 1,666 MHz hydroxyl line.

When it comes to extraterrestrial life, our mantra has always been to “follow the water.” But now, it seems, astronomers are turning their eyes away from water and toward methane — the simplest organic molecule, also widely accepted to be a sign of potential life.

Astronomers at the University College London (UCL) and the University of New South Wales have created a powerful new methane-based tool to detect extraterrestrial life, more accurately than ever before.

In recent years, more consideration has been given to the possibility that life could develop in other mediums besides water. One of the most interesting possibilities is liquid methane, inspired by the icy moon Titan, where water is as solid as rock and liquid methane runs through the river valleys and into the polar lakes. Titan even has a methane cycle.

Astronomers can detect methane on distant exoplanets by looking at their so-called transmission spectrum. When a planet transits, the star’s light passes through a thin layer of the planet’s atmosphere, which absorbs certain wavelengths of the light. Once the starlight reaches Earth it will be imprinted with the chemical fingerprints of the atmosphere’s composition.

But there’s always been one problem. Astronomers have to match transmission spectra to spectra collected in the laboratory or determined on a supercomputer. And “current models of methane are incomplete, leading to a severe underestimation of methane levels on planets,” said co-author Jonathan Tennyson from UCL in a press release.

So Sergei Yurchenko, Tennyson and colleagues set out to develop a new spectrum for methane. They used supercomputers to calculate about 10 billion lines — 2,000 times bigger than any previous study. And they probed much higher temperatures. The new model may be used to detect the molecule at temperatures above that of Earth, up to 1,500 K.

“We are thrilled to have used this technology to significantly advance beyond previous models available for researchers studying potential life on astronomical objects, and we are eager to see what our new spectrum helps them discover,” said Yurchenko.

The tool has already successfully reproduced the way in which methane absorbs light in brown dwarfs, and helped correct our previous measurements of exoplanets. For example, Yurchenko and colleagues found that the hot Jupiter, HD 189733b, a well-studied exoplanet 63 light-years from Earth, might have 20 times more methane than previously thought.

The paper has been published in the Proceedings of the National Academy of Sciences and may be viewed here.

India’s First Mars Probe ‘MOM’ Blasts Free of Earth Joining MAVEN in Race to Red Planet

CAPE CANAVERAL, FL – India’s first ever Mars probe ‘MOM’ successfully fired its main engine today (Dec. 1), blasting the craft free of the Earth’s sphere of influence forever to begin her nearly yearlong momentous voyage to the Red Planet.

Indian space engineers initiated the 440 Newton liquid fueled engine firing precisely as planned at 00:49 hrs (IST) on Sunday, Dec. 1, 2013 during a critical nail-biting burn lasting some 22 minutes.

The Trans Mars Insertion (TMI) firing propelled India’s Mars Orbiter Mission (MOM) away from Earth forever and placed the spacecraft on course for a rendezvous with the Red Planet on September 24, 2014 – where it will study the atmosphere and sniff for signals of methane.

Sunday’s Mars insertion burn imparted the vehicle with an incremental velocity of 647.96 meters per second (m/sec) consuming 198 kg of fuel.

Trans Mars Injection (TMI), carried out on Dec 01, 2013 at 00:49 hrs (IST) has moved the spacecraft in the Mars Transfer Trajectory (MTT). With TMI the Earth orbiting phase of the spacecraft ended and the spacecraft is now on a course to encounter Mars after a journey of about 10 months around the Sun. Credit: ISRO
Trans Mars Injection (TMI), carried out on Dec 01, 2013 at 00:49 hrs (IST) has moved the spacecraft in the Mars Transfer Trajectory (MTT). With TMI the Earth orbiting phase of the spacecraft ended and the spacecraft is now on a course to encounter Mars after a journey of about 10 months around the Sun. Credit: ISRO

The maneuver dubbed ‘The mother of all slingshots’, enabled MOM to finally achieve escape velocity and catapulted the 1,350 kilogram (2,980 pound) spacecraft on an historic flight streaking towards Mars.

And in a rare but rather delightful coincidence, MOM is not alone on her remarkable Martian sojourn. Following the triumphant engine burn, she now joins NASA’s MAVEN orbiter in a gallant marathon race to the Red Planet.

MOM was designed and developed by the Indian Space Research Organization’s (ISRO) at a cost of $69 Million and marks India’s inaugural foray into interplanetary flight.

“The Earth orbiting phase of the spacecraft ended,” with this maneuver said ISRO.

MOM is healthy and all systems are functioning normally.

While MOM was cycling Earth, ISRO scientists and engineers activated and tested the probes systems and science payloads.

They also turned the crafts color camera homewards to capture the “First ever image of Earth Taken by Mars Color Camera,” according to ISRO.

First ever image of Earth Taken by Mars Color Camera aboard India’s Mars Orbiter Mission (MOM) spacecraft currently orbiting Earth prior to upcoming Trans Mars Insertion. Image is focused on the Indian subcontinent.  Credit: ISRO
First ever image of Earth Taken by Mars Color Camera aboard India’s Mars Orbiter Mission (MOM) spacecraft currently orbiting Earth prior to upcoming Trans Mars Insertion. Image is focused on the Indian subcontinent. Credit: ISRO

MOM is nicknamed ‘Mangalyaan’ – which in Hindi means ‘Mars craft.’

MOM’s journey bagen with a picture perfect Nov. 5 liftoff atop India’s highly reliable four stage Polar Satellite Launch Vehicle (PSLV) C25 from ISRO’s Satish Dhawan Space Centre SHAR, Sriharikota.

The PSLV booster precisely injected MOM into an initial elliptical Earth parking orbit of 247 x 23556 kilometers with an inclination of 19.2 degrees.

PSLV does not have sufficient thrust to send MOM streaking directly to the Red Planet.

Therefore since the flawless launch, the engine has been fired 6 times on November 7, 8, 9, 11, and 16 plus one supplementary maneuver to gradually raise the spacecrafts apogee from 23556 km to 192,874 km.

The most recent orbit raising maneuver occurred on Nov 16, 2013 with a burn time of 243.5 seconds and increased the apogee from 118,642 km to 192,874 km.

Liquid fueled engine fires and successfully propels MOM into Mars Transfer Trajectory on Dec. 1, 2013 and India into interplanetary space !  Credit: ISRO
Liquid fueled engine fires and successfully propels MOM into Mars Transfer Trajectory on Dec. 1, 2013 and India into interplanetary space ! Credit: ISRO

Today’s burn was the final one around Earth and absolutely crucial for setting her on course for Mars.

MOM was the first of two missions dispatched to Mars by Earthlings this November.

Half a world away, NASA’s MAVEN orbiter blasted off on Nov. 18 from Cape Canaveral Air Force Station, Florida atop an Atlas V booster on a direct path to the Red Planet.

The MOM spacecraft is now on traveling on a heliocentric elliptical trajectory to begin a 300 day long interplanetary voyage of more than 700 Million kilometers (400 Million miles) to the Red Planet.

Along the path to Mars, ISRO plans to conduct a series of Trajectory Correction Maneuvers (TCMs) using MOM’s Attitude and Orbit Control System (AOCS) thrusters to precisely navigate the probe to the point required to achieve orbit around the Red Planet

Following the ten month cruise through space the orbital insertion engine will fire for a do or die burn on September 24, 2014 placing MOM into an 377 km x 80,000 km elliptical orbit around Mars.

MOM will reach Mars vicinity just two days after MAVEN’s arrival on Sept. 22, 2014.

If all continues to goes well, India will join an elite club of only four who have launched probes that successfully investigated the Red Planet from orbit or the surface – following the Soviet Union, the United States and the European Space Agency (ESA).

Both MAVEN and MOM’s goal is to study the Martian atmosphere, unlock the mysteries of its current atmosphere and determine how, why and when the atmosphere and liquid water was lost – and how this transformed Mars climate into its cold, desiccated state of today.

Although MOM’s main objective is a demonstration of technological capabilities, the probe is equipped with five indigenous instruments to conduct meaningful science – including a multi color imager and a methane gas sniffer to study the Red Planet’s atmosphere, morphology, mineralogy and surface features. Methane on Earth originates from both geological and biological sources – and could be a potential marker for the existence of Martian microbes.

MOM’s 15 kg (33 lb) science suite comprises:

MCM: the tri color Mars Color Camera images the planet and its two tiny moons, Phobos and Deimos

LAP: the Lyman Alpha Photometer measures the abundance of hydrogen and deuterium to understand the planets water loss process

TIS: the Thermal Imaging Spectrometer will map surface composition and mineralogy

MENCA: the Mars Exospheric Neutral Composition Analyser is a quadrapole mass spectrometer to analyze atmospheric composition

MSM: the Methane Sensor for Mars measures traces of potential atmospheric methane down to the ppm level.

Scientists will be paying close attention to whether MOM detects any atmospheric methane to compare with measurements from NASA’s Curiosity rover – which found ground level methane to be essentially nonexistent – and Europe’s upcoming 2016 ExoMars Trace Gas Orbiter.

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India’s MOM – ‘Mangalyaan’ mission is expected to continue gathering measurements at the Red Planet for at least six months and hopefully much longer.

MAVEN could operate for a decade or longer and is also crucial for relaying images and data collected by NASA’s current and upcoming surface rovers and landers.

Although they were developed independently and have different suites of scientific instruments, the MAVEN and MOM science teams will “work together” to unlock the secrets of Mars atmosphere and climate history, MAVEN’s top scientist told Universe Today.

“We have had some discussions with their science team, and there are some overlapping objectives,” Bruce Jakosky told me. Jakosky is MAVEN’s principal Investigator from the University of Colorado at Boulder.

“At the point where we [MAVEN and MOM] are both in orbit collecting data we do plan to collaborate and work together with the data jointly,” Jakosky said.

Stay tuned here for continuing MOM and MAVEN news and Ken’s MAVEN and SpaceX Falcon 9 launch reports from on site at the Kennedy Space Center press center and Cape Canaveral Air Force Station, Florida.

Ken Kremer

MOM’s Last Night on Earth; Midnight Marvel for India’s Mars Mission – Live Webcast

It’ s a Mind-Blowing Midnight Marvel !
India’s fueled PSLV rocket and Mars Orbiter Mission (MOM) await Nov. 5 blastoff at 14:38 hrs IST (9:08 UTC, 4:08 a.m. EST). Credit: ISRO.
Watch ISRO’s Live Webcast[/caption]

MOM is spending her last night on Earth – and she’s a Mind-Blowing Midnight Marvel !

The pride of all India, and everyone’s favorite MOM is healthy and set to embark on the nation’s first ever interplanetary voyage of exploration. She aims to conduct a detailed study of the Martian atmosphere and sniff for methane – a potential indicator for life.

The Mars Orbiter Mission (MOM) was designed and developed by the Indian Space Research Organization (ISRO) which is broadcasting a live webcast of the launch starting at 14:00 hrs IST, 3:30 a.m. EST at – http://isro.org/

“All vehicle systems have been switched ON,” as of now, says ISRO.

Now less than 8 hours from blastoff, the PSLV-C25 booster rocket is fully fueled and poised to streak from ISRO’s Satish Dhawan Space Centre SHAR, Sriharikota, located on India’s east coast in Andhra Pradesh state.

If all goes well with MOM, India joins an elite club of four who have launched probes that successfully investigated the Red Planet from orbit or the surface – following the Soviet Union, the United States and the European Space Agency (ESA).

Reaching Mars successfully is an enormous technological challenge. More than half of all Earth’s attempts have failed. But those who fail to ‘dare mighty things’ are doomed to timidity and ignominy.

Gorgeous view of the majestic Polar Satellite Launch Vehicle, PSLV C25 with its passenger, the Indian Space Research Organization’s (ISRO's) Mars Orbiter Mission (MOM) spacecraft inside. The Mobile service tower is also seen in the background.  Credit: IRSO
Gorgeous view of the majestic Polar Satellite Launch Vehicle, PSLV C25 with its passenger, the Indian Space Research Organization’s (ISRO’s) Mars Orbiter Mission (MOM) spacecraft inside. The Mobile service tower is also seen in the background. Credit: IRSO

ISRO reports that the weather outlook is favorable for an on time launch on Nov 05, 2013 at 14:38 hrs IST (9:08 UTC, 4:08 a.m. EST).

“Weather Forecast for launch day based on today’s image from Kalpana Meteorological Satellite: Early morning, cloudy and low probability of Rain, No severe weather expected. During launch window – partly cloudy weather and no rain is expected.”

“Looks like we are heading towards a bright and sunny day for the launch,” says ISRO.

Today's weather image from India’s Kalpana Meteorological Satellite. Credit: ISRO
Today’s weather image from India’s Kalpana Meteorological Satellite. Credit: ISRO

Just hours ago the final loading of propellants into the rocket’s liquid fueled second stage (PS2) with highly toxic nitrogen tetroxide and hydrazine was satisfactorily completed.

The launch gantry has been retracted to a distance of 50 meters and the 44 meter (144 foot) tall four stage PSLV booster stands at the ready under the gaze of the starry night.

Two tracking ships – SCI Nalanda and SCI Yamuna – have been deployed to the Indian Ocean.

They are now in position to relay critical in flight telemetry during the ignition of the PSLV-C25 fourth stage and the spacecraft’s separation from the rocket at T plus 44 minutes.

“For about ten minutes between the separation of third stage of PSLV and ignition of fourth stage the vehicle will not be visible from any ground stations as will be evident in the Live telecast,” says ISRO.

Tracking MOM !  Credit: ISRO
Tracking MOM ! Credit: ISRO

And the launch team is leaving no stone unturned to ensure success!

“As the country gets embraced in deep sleep – don’t forget a few hundred tireless minds at ISRO – rock-steady on their consoles and keeping their strict vigil on the several health parameters of the rocket and the MoM spacecraft,” said ISRO in a statement.

And here’s a poetic tribute to MOM from ISRO

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MOM is the first of two new Mars orbiter science probes from Earth set to blast off for the Red Planet this November. On the other side of Earth, NASA’s MAVEN orbiter remains on target to launch barely two weeks after MOM on Nov. 18 – from Cape Canaveral, Florida.

The 1,350 kilogram (2,980 pound) MOM orbiter is also known as‘Mangalyaan’ – which in Hindi means ‘Mars craft.’

‘Mangalyaan’ is outfitted with an array of five indigenous science instruments including a multi color imager and a methane gas sniffer to study the Red Planet’s atmosphere, morphology, mineralogy and surface features. Methane on Earth originates from both geological and biological sources – and could be a potential marker for the existence of Martian microbes.

The PSLV will inject MOM into an initially elliptical Earth parking orbit of 248 km x 23,500 km. A series of six orbit raising burns will eventually place MOM on a trajectory to Mars around December 1.

Tracking the MOM Mission! A complex network of ground stations, as indicated in the image, has been laid out for keeping an eye on the various phases of PSLV-C25/ ISRO's Mars Orbiter Mission, including the launch, Earth bound maneuvers, Heliocentric phase as well as the Martian phase.  Additionally, two ship borne terminals have also been deployed in the southern Pacific Ocean to cover critical events during the launch phase. After satellite separation from the launch vehicle, the Spacecraft  operations are controlled from the Spacecraft Control Centre of ISRO Telemetry, Tracking And Command Network (ISTRAC) in Bangalore.
Tracking the MOM Mission!
A complex network of ground stations, as indicated in the image, has been laid out for keeping an eye on the various phases of PSLV-C25/ ISRO’s Mars Orbiter Mission, including the launch, Earth bound maneuvers, Heliocentric phase as well as the Martian phase. Additionally, two ship borne terminals have also been deployed in the southern Pacific Ocean to cover critical events during the launch phase. After satellite separation from the launch vehicle, the Spacecraft operations are controlled from the Spacecraft Control Centre of ISRO Telemetry, Tracking And Command Network (ISTRAC) in Bangalore.

Following a 300 day interplanetary cruise phase, the do or die orbital insertion engine will fire on September 24, 2014 and place MOM into an 366 km x 80,000 km elliptical orbit.

MOM and MAVEN both arrive in Mars orbit within days of one another next September – joining Earth’s invasion fleet of five operational orbiters and intrepid surface rovers currently unveiling the mysteries of the Red Planet.


MAVEN’s goal
is to study Mars atmosphere in unprecedented detail. The MAVEN and MOM science teams will “work together” to unlock the secrets of Mars atmosphere, MAVEN’s top scientist told Universe Today.

“We have had some discussions with their science team, and there are some overlapping objectives,” Bruce Jakosky told me. Jakosky is MAVEN’s principal Investigator from the University of Colorado at Boulder.

“At the point where we [MAVEN and MOM] are both in orbit collecting data we do plan to collaborate and work together with the data jointly,” Jakosky said.

Godspeed MOM !

Ken Kremer

Pictures From T-86: Cassini’s Latest Flyby of Titan

On September 26-27 Cassini executed its latest flyby of Titan, T-86, coming within 594 miles (956 km) of the cloud-covered moon in order to measure the effects of the Sun’s energy on its dense atmosphere and determine its variations at different altitudes.

The image above was captured as Cassini approached Titan from its night side, traveling about 13,000 mph (5.9 km/s). It’s a color-composite made from three separate raw images acquired in red, green and blue visible light filters.

Titan’s upper-level hydrocarbon haze is easily visible as a blue-green “shell” above its orange-colored clouds.

Cassini captured this image as it approached Titan’s sunlit limb, grabbing a better view of the upper haze. Some banding can be seen in its highest reaches.

The haze is the result of UV light from the Sun breaking down nitrogen and methane in Titan’s atmosphere, forming hydrocarbons that rise up and collect at altitudes of 300-400 kilometers. The sea-green coloration is a denser photochemical layer that extends upwards from about 200 km altitude.

In this image, made from data acquired on Sept. 27, Titan’s south polar vortex can be made out just within the southern terminator. The vortex is a relatively new feature in Titan’s atmosphere, first spotted earlier this year. It’s thought that it’s a region of open-cell convection forming above the moon’s pole, a result of the approach of winter to Titan’s southern half.

Read: Cassini Spots Surprising Swirls Above Titan’s South Pole

This T-86 flyby was was one of a handful of opportunities to profile Titan’s ionosphere from the outermost edge of Titan’s atmosphere. In addition Cassini was able to look for any changes to Ligeia Mare, a methane lake last observed in spring of 2007.

Now that Titan has been under scrutiny for a full year of Saturn’s seasons — which lasts 29.7 Earth-years — astronomers now know that varying amounts of solar radiation can drastically change situations both within Saturn’s atmosphere and on its surface.

“As with Earth, conditions on Titan change with its seasons. We can see differences in atmospheric temperatures, chemical composition and circulation patterns, especially at the poles,” said Dr. Athena Coustenis from the Paris-Meudon Observatory in France. “For example, hydrocarbon lakes form around the north polar region during winter due to colder temperatures and condensation. Also, a haze layer surrounding Titan at the northern pole is significantly reduced during the equinox because of the atmospheric circulation patterns. This is all very surprising because we didn’t expect to find any such rapid changes, especially in the deeper layers of the atmosphere.”

“It’s amazing to think that the Sun still dominates over other energy sources even as far out as Titan, over 1.5 billion kilometres from us.”
– Dr. Athena Coustenis, Paris-Meudon Observatory

The image above, acquired on Sept. 28, was added to this post on Oct. 1. It was taken from a distance of  649,825 miles (1,045,792 kilometers.)

Cassini’s next targeted approach to Titan — T-87 — will occur on November 13.

Get more news from the Cassini mission here.

Image credits: NASA/JPL/Space Science Institute. All color composites by Jason Major. Images have not been validated or calibrated by the SSI team.

 

(Do you love the Cassini mission as much as we do? Vote on your favorite Cassini “Shining Moment” here, in honor of the 15th anniversary of Cassini’s launch on October 15! Amazing to think it’s already been 15 years — 8 of those in orbit around Saturn!)

Could Dust Devils Create Methane in Mars’ Atmosphere?

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Methane on Mars has long perplexed scientists; the short-lived gas has been measured in surprising quantities in Mars’ atmosphere over several seasons, sometimes in fairly large plumes. Scientists have taken this to be evidence of Mars being an ‘active’ planet, either geologically or biologically. But a group of researchers from Mexico have come up with a different – and rather unexpected – source of methane: dust storms and dust devils.

“We propose a new production mechanism for methane based on the effect of electrical discharges over iced surfaces,” reports a paper published in Geophysical Research letters, written by a team led by Arturo Robledo-Martinez from the Universidad Autónoma Metropolitana, Azcapotzalco, Mexico.

“The discharges, caused by electrification of dust devils and sand storms, ionize gaseous CO2 and water molecules and their byproducts recombine to produce methane.”

Graph from the paper Electrical discharges as a possible source of methane on Mars: Lab simulation, Geophys. Res. Lett., 39, L17202, doi:10.1029/2012GL053255.

In a laboratory simulation, they showed that that pulsed electrical discharges over ice samples in a synthetic Martian atmosphere produced about 1.41×1016 molecules of methane per joule of applied energy. The results of the electrical discharge experiment were compared with photolysis induced with UV laser radiation and it was found that both produce methane, although the efficiency of photolysis is one-third of that of the discharge.

The scientists don’t rule out that methane may indeed come from other sources as well, but the way that dust devils and storms can quickly form means they can also quickly generate methane. “The present mechanism may be acting in parallel with other proposed sources but its main advantage is that it can generate methane very quickly and thus explain the generation of plumes,” the team writes.

Methane has been observed in Mars’ atmosphere since 1999, but in 2009, scientists studying the atmosphere of Mars over several Martian years with telescopes here on Earth announced they had found three regions of active release of methane over areas that had evidence of ancient ground ice or flowing water.

They observed and mapped multiple plumes of methane on Mars, one of which released about 19,000 metric tons of methane. The plumes were emitted during the warmer seasons — spring and summer — which is also when dust devils tend to form.

Methane on Mars is enticing because it only lasts a few hundred years in Mars’ atmosphere, meaning it has to be continually replaced. And in the back of everyone’s minds has been the possibility of some sort of Martian life producing it.

“Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane … indicates some ongoing process is releasing the gas,” said Dr. Michael Mumma of NASA’s Goddard Space Flight Center in Greenbelt, Md in 2009. “At northern mid-summer, methane is released at a rate comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, Calif.”

The researchers in 2009 thought that the methane was being released from Mars’ interior, perhaps because the permafrost blocking cracks and fissures vaporized, allowing methane to seep into the Martian air.

The unknown has been where the methane has been coming from; if it is being released from the interior, it could be produced by either geologic processes such as serpentinization, a simple water/rock reaction or biologic processes of microbes (or something bigger) releasing methane as a waste product.

But if dust devils and dust storms can also produce methane, the mystery becomes a little more mundane.

The new research by the team from Mexico also mentioned fissures in the surface, but for a different reason, saying that the electric field of dust devils is amplified by the topology of the soil: “The electrical field produced by a dust devil can not only overcome the weak dielectric strength of the Martian atmosphere, but also penetrate into cracks on the soil and so reach the ice lying at the bottom, with added strength, due to the topography of the terrain,” the team wrote.

At a concentration of about 10 to 50 parts per billion by volume, methane is still a trace element in the Martian atmosphere, and indeed the sharp variations in its concentration that have been observed have been difficult to explain. Hopefully the research teams can coordinate follow-up observations of methane production during the dust devil and dust storm seasons on Mars.

Read the team’s abstract.

Read our article from 2009 about Mars Methane.

African Lake Has a Twin on Titan

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A large lake on Saturn’s cloud-covered Titan seems very similar to the Etosha Pan, a salt-encrusted dry lakebed in northern Namibia that periodically fills with water. As it turns out, Titan’s “great lake” may also be temporary.

Ontario Lacus, so named because of its similarity both in shape and size to Lake Ontario here on Earth, was first discovered near the south pole of Titan by the Cassini spacecraft in 2009. Its smooth, dark appearance in radar images indicated a uniform and reflective surface, implying a large — although likely shallow — body of liquid.

Of course, on Titan the liquid isn’t water — it’s methane, which is the main ingredient of the hydrologic cycle found on the giant moon. That far from the Sun the temperatures at Titan’s poles fall to a frigid -300ºF (-185ºC), much too cold for water to exist as a liquid and so, on this world, methane has taken its place.

A research team led by Thomas Cornet of the Université de Nantes, France has taken a closer look at Cassini’s radar data of Ontario Lacus and found evidence of channels carved into the southern portion. According to the team, this likely indicates that the lakebed surface is exposed.

Cassini image of Ontario Lacus. (NASA/JPL/SSI)

“We conclude that the solid floor of Ontario Lacus is most probably exposed in those areas,” said Cornet.

In addition, sediment layers surrounding the lake suggest that the liquid level has varied.

All in all, this reveals a striking resemblance between Ontario Lacus and Namibia’s Etosha Pan — an “ephemeral lake” that is dry for much of the year, occasionally filling with a shallow layer of water which evaporates, leaving salty rings of sediment.

The inherent otherworldly nature of Etosha Pan is further underlined — and perhaps foreshadowed! — by its use as a backdrop in the 1968 sci-fi film 2001: A Space Odyssey.

Although Ontario Lacus was initially thought to be permanently filled with liquid hydrocarbons, the team’s findings draw a strong correlation with this well-known Earthly environment, suggesting a much more temporary nature and showing the value of comparative research.

Satellite image of Etosha Pan, acquired on April 28, 2012. (Chelys/EOSnap)

“These results emphasise the importance of comparative planetology in modern planetary sciences,” said Nicolas Altobelli, Cassini project scientist for ESA.”Finding familiar geological features on alien worlds like Titan allows us to test the theories explaining their formation.”

Read the press release from ESA here.

Image credits: Cassini radar image JPL/NASA. Envisat radar image ESA. Composite image: LPGNantes.

Mars 2016 Methane Orbiter: Searching for Signs of Life

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The new joint Mars exploration program of NASA and ESA is quickly pushing forward to implement an agreed upon framework to construct an ambitious new generation of red planet orbiters and landers starting with the 2016 and 2018 launch windows.

The European-led ExoMars Trace Gas Mission Orbiter (TGM) has been selected as the first spacecraft of the joint initiative and is set to launch in January 2016 aboard a NASA supplied Atlas 5 rocket for a 9 month cruise to Mars. The purpose is to study trace gases in the martian atmosphere, in particular the sources and concentration of methane which has significant biological implications. Variable amounts of methane have been detected by a martian orbiter and ground based telescopes on earth. The orbiter will likely be accompanied by a small static lander provided by ESA and dubbed the Entry, Descent and Landing Demonstrator Module (EDM).

The NASA Mars Program is shifting its science strategy to coincide with the new joint venture with ESA and also to build upon recent discoveries from the current international fleet of martian orbiters and surface explorers Spirit, Opportunity and Phoenix (see my earlier mars mosaics). Doug McCuiston, NASA’s director of Mars Exploration at NASA HQ told me in an interview that, “NASA is progressing quickly from ‘Follow the Water’ through assessing habitability and on to a theme of ‘Seeking the Signs of Life’. Looking directly for life is probably a needle in the haystack, but the signatures of past or present life may be more wide spread through organics, methane sources, etc”.

NASA and ESA will issue an “Announcement of Opportunity for the orbiter in January 2010” soliciting proposals for a suite of science instruments according to McCuiston. “The science instruments will be competitively selected. They are open to participation by US scientists who can also serve as the Principal Investigators (PI’s)”. Proposals are due in 3 months and will be jointly evaluated by NASA and ESA. Instrument selections are targeted for announcement in July 2010 and the entire cost of the NASA funded instruments is cost capped at $100 million.

Mars Trace Gas Mission orbiter slated for 2016 launch is the first spacecraft in the new ESA & NASA Mars Exploration Joint Initiative. Credit: NASA ESA
Mars Trace Gas Mission orbiter slated for 2016 launch is the first spacecraft in the new ESA & NASA Mars Exploration Joint Initiative. Credit: NASA ESA

“The 2016 mission must still be formally approved by NASA after a Preliminary Design Review, which will occur either in late 2010 or early 2011. Funding until then is covered in the Mars Program’s Next Decade wedge, where all new-start missions reside until approved, or not, by the Agency”, McCuiston told me. ESA’s Council of Ministers just gave the “green light” and formally approved an initial budget of 850 million euros ($1.2 Billion) to start implementing their ExoMars program for the 2016 and 2018 missions on 17 December at ESA Headquarters in Paris, France. Another 150 million euros will be requested within two years to complete the funding requirement for both missions.

ESA has had to repeatedly delay its own ExoMars spacecraft program since it was announced several years ago due to growing complexity, insufficient budgets and technical challenges resulting in a de-scoping of the science objectives and a reduction in weight of the landed science payload. The ExoMars rover was originally scheduled to launch in 2009 and is now set for 2018 as part of the new architecture.

The Trace Gas orbiter combines elements of ESA’s earlier proposed ExoMars orbiter and NASA’s proposed Mars Science Orbiter. As currently envisioned the spacecraft will have a mass of about 1100 kg and carry a roughly 115 kg science payload, the minimum deemed necessary to accomplish its goals. The instruments must be highly sensitive in order to be capable of detecting the identity and extremely low concentration of atmospheric trace gases, characterizing the spatial and temporal variation of methane and other important species, locating the source origin of the trace gases and determining if they are caused by biologic or geologic processes. Current photochemical models cannot explain the presence of methane in the martain atmosphere nor its rapid appearance and destruction in space, time or quantity.

An Atlas rocket similar to this vehicle I observed at Cape Canaveral Pad 41 is projected to launch the 2016 Mars orbiter. Credit: Ken Kremer
An Atlas rocket similar to this vehicle I observed at Cape Canaveral Pad 41 is projected to launch the 2016 Mars orbiter. Credit: Ken Kremer

Among the instruments planned are a trace gas detector and mapper, a thermal infrared imager and both a wide angle camera and a high resolution stereo color camera (1 – 2 meter resolution). “All the data will be jointly shared and will comply with NASA’s policies on fully open access and posting into the Planetary Data System”, said McCuiston.
Another key objective of the orbiter will be to establish a data relay capability for all surface missions up to 2022, starting with 2016 lander and two rovers slotted for 2018. This timeframe could potentially coincide with Mars Sample Return missions, a long sought goal of many scientists.

If the budget allows, ESA plans to piggyback a small companion lander (EDM) which would test critical technologies for future missions. McCuiston informed me that, “The objective of this ESA Technology Demonstrator is validating the ability to land moderate payloads, so the landing site selection will not be science-driven. So expect something like Meridiani or Gusev—large, flat and safe. NASA will assist ESA engineering as requested, and within ITAR constraints.” EDM will use parachutes, radar and clusters of pulsing liquid propulsion thrusters to land.

“ESA plans a competitive call for instruments on their 3-4 kg payload”, McCuiston explained. “The Announcement of Opportunity will be open to US proposers as well so there may be some US PI’s. ESA wants a camera to ‘prove’ they got to the ground. Otherwise there is no significant role planned for NASA in the EDM”.

The lander would likely function as a weather station and be relatively short lived, perhaps 8 Sols or martian days, depending on the capacity of the batteries. ESA is not including a long term power source, such as from solar arrays, so the surface science will thus be limited in duration.

The orbiter and lander would separate upon arrival at Mars. The orbiter will use a series of aerobraking maneuvers to eventually settle into a 400 km high circular science orbit inclined at about 74 degrees.

The joint Mars architecture was formally agreed upon last summer at a bilateral meeting between Ed Weiler (NASA) and David Southwood (ESA) in Plymouth, UK. Weiler is NASA’s Associate Administrator for the Science Mission Directorate and Southwood is ESA’s Director of Science and Robotic Exploration. They signed an agreement creating the Mars Exploration Joint Initiative (MEJI) which essentially weds the Mars programs of NASA and ESA and delineates their respective program responsibilities and goals.

“The key to moving forward on Mars exploration is international collaboration with Europe”, Weiler said to me in an interview. “We don’t have enough money to do these missions separately. The easy things have been done and the new ones are more complex and expensive. Cost overruns on Mars Science Lab (MSL) have created budgetary problems for future mars missions”. To pay for the MSL overrun, funds have to be taken from future mars budget allocations from fiscal years 2010 to 2014.

“2016 is a logical starting point to work together. NASA can have a 2016 mission if we work with Europe but not if we work alone. We can do so much more by working together since we both have the same objectives scientifically and want to carry out the same types of mission”. Weiler and Southwood instructed their respective science teams to meet and lay out a realistic and scientifically justifiable approach. Weiler explained to me that his goal and hope was to reinstate an exciting Mars architecture with new spacecraft launching at every opportunity which occurs every 26 months and which advance the state of the art for science. “It’s very important to demonstrate a critical new technology on each succeeding mission”.

More on the 2018 mission plan and beyond in a follow up report.

Mars from orbit.  Valles Marineris and Volcanic region
Mars from orbit. Valles Marineris and Volcanic region