Category Archives: Space Sunday

Space update special: the 7-exoplanet system

An artist's impression of the sky from the outermost of the three TRAPPIST exoplanets in the star's habitable zone (see the 360-video below)

An artist’s impression of the sky from the outermost of the three TRAPPIST exoplanets in the star’s habitable zone (see the 360-video below). Credit: NASA

On Wednesday, February 22nd, US space agency NASA, working with a team of European astronomers, confirmed no fewer than seven extra-solar planets are orbiting a star some 39 light years away – with three of them within the so-called “Goldilocks zone” of habitability.

The star in question is TRAPPIST-1, named for the instruments used in its discovery, the Transiting Planets and Planetesimals Small Telescope (TRAPPIST),  and more formally known as 2MASS J23062928-0502285. Regular readers of my Space Sunday column might remember that I referred to the system back in November 2016, whilst discussing the James Webb Space Telescope and the hunt of exoplanets. The NASA announcement, which coincides with the publication of a new paper by the TRAPPIST team, adds dramatic new information to the distant star system.

The first two of the planets orbiting the star were located in May 2016, after the TRAPPIST team had studied the results of a continuous series of observations of the star between September and December 2015 using the telescope, located at the European Southern Observatory’s (ESO) La Silla Observatory in Chile.

Artist’s concept showing what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances. Credit: NASA

Artist’s concept showing what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances. Credit: NASA

What was intriguing about the two world was that not only were both within the so-called “Goldilocks zone” of their parent planet, where conditions might be “just right” for life to start, but both were roughly comparable to Earth in size, and therefore likely solid bodies, and spectral analysis suggested both have atmospheres.

A third planet, TRAPPIST-1d was also discovered the the same time, but it was behaving oddly. This prompted a further extended period of observation between September and October 2016, using both the ESO’s ground-based Very Large Telescope, and the Spitzer Space Telescope. This work revealed at “TRAPPIST-1d” was not one, but three worlds, again, all roughly in the Earth-sized category. Spitzer’s data additionally revealed two more planets of roughly the same size, taking the total to seven. Following this, Hubble turned its attention on the planets, looking for signs of hydrogen and helium – the chemical signatures that would indicate if any of them might be gas giants. It found none, further confirming they are likely rocky in nature.

The size, mass and density of these telluric worlds were obtained by measuring the periodic dips in TRAPPIST-1’s luminosity as a result of each of the planets passing in front of it. This allowed the international team studying the system to further assess whether each world was rocky, icy, or gaseous and determine which might be habitable.

trappist-1-3

Via: Space.com. Click for full size

TRAPPIST-1 is an ultra-cool red dwarf star only slightly larger than the planet Jupiter, and about 2,000 times dimmer than the sun.

Such stars, designated Class M, are the most frequent type of star in the Universe – making up an estimated 70% of stars in our galaxy alone. However, they do not radiate energy like our own sun, instead they are very volatile; all activity within them is entirely convective in nature, giving rise to massive stellar flares.

Given TRAPPIST-1 is so small, all of its planets orbit in very close proximity to it – closer than Mercury is to the Sun (the nearest orbits its parent star once every 1.5 terrestrial days, and the outermost, about once every 20 terrestrial days). This makes them very vulnerable to violent outbursts by the star, and could affect their surface conditions and their ability to retain an atmosphere.

This close proximity also means all of the planets are tidally locked – they always have the same side facing their sun. Thus they all are likely to have extremes of temperature, and those with an atmosphere are likely to have quite extreme weather as well. However – and conversely – it also means they could have the potential for liquid water to exist on their surfaces.

The innermost of the three planets in the habitable zone, TRAPPIST-1e, is very close in size to Earth, and receives about the same amount of light as Earth does, and may well have similar day time temperatures. The middle planet of the three, TRAPPIST-1f, meanwhile, might be a water rich world, also roughly the same size as Earth. It has a 9-day orbit, and receives about the same amount of light from its sun as Mars does from our own.

Another artist's impression of how the TRAPPIST system might look from the surface of one of the worlds - assuming they have liquid water present

Another artist’s impression of how the TRAPPIST system might look from the surface of one of TRAPPIST-1f, the middle one of the three planets in the star’s habitable zone – assuming it has liquid water present. Credit: NASA

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Space Sunday: Jupiter, Enceladus and Ceres; SLS, SpaceX and Dream Chaser

This stunning enhanced colour images of Jupiter's south polar region was captured by the JunoCam instrument aboard the Juno spacecraft on February 2nd, 2017. It reveals a complex series of interactions occurring in the fast-spinning atmosphere

This stunning enhanced colour images of Jupiter’s south polar region was captured by the JunoCam instrument aboard the Juno spacecraft on February 2nd, 2017. It reveals a complex series of interactions occurring in the fast-spinning atmosphere. Credit: NASA/JPL / SwRI

Following its latest close flyby of Jupiter – passing just 4,200 km (2,600 mi) above the gas giant’s cloud tops on February 2nd, 2017, NASA’s Juno mission spacecraft is now heading away from the planet once more and the next of its 53.5 day orbits. As I’ve previously reported in these Space Sunday columns, the original plan had been to use one of these close passes over the planet (October 2016), in conjunction with a sustained burn of the spacecraft’s British-built rocket motor, to move it into a short, 14-day period orbit around Jupiter.

However, a potential fault detected within the engine system meant the October burn was cancelled, and since then, engineers had been trying to assess if the issue  – a set of faulty valves – could be overcome, and the consequences of attempting an additional engine burn if not. No definitive answer has been found and so, following the February 2nd flyby, the decision was taken to cancel all plans for the engine burn and leave the spacecraft in its current 53.5 day orbit around Jupiter.

Doing so doesn’t compromise the overall mission objectives, but it does reduce the number of close passes over Jupiter the vehicle can make. If the reduced orbital period had been possible, the spacecraft would have made some 30 close flybys over Jupiter’s cloud tops during the primary mission period, set to end in July 2018. Remaining in the 53.5 day orbit means it will only make around 12 such close flybys in the same period.

The Juno spacecraft was supposed to complete two 53-day orbits around Jupiter, then lower its orbit Oct. 19 to fly around the planet once every 14 days. That engine burn has been postponed. Credit: NASA / JPL

The Juno spacecraft was supposed to complete two 53.5-day orbits around Jupiter in July and August 2016 (shown in green), before using its main engine to brake itself into a 14-primary science orbit (shown in blue). Due to continued concerns about the vehicle’s engine unit, the decisions has now been made to leave it in the 53.5 day orbit. Credit: NASA / JPL

A positive point with the spacecraft remaining in its more extended orbit is that it will spend less time within the harsher regions of Jupiter’s radiation belts, and could thus remain active for longer than the primary mission period – and mission planners are already considering applying for further funding to allow the mission to extend beyond July 2018. It also means that the spacecraft will be able to engage in additional science activities.

The close encounters with Jupiter have already allowed the spacecraft to probe deep within the planet’s cloud belts and discover they extend far deeper into the planet’s atmosphere than had been imagined, and that Jupiter’s magnetic field and auroras are more powerful than previously thought.

“Juno is providing spectacular results, and we are rewriting our ideas of how giant planets work,” Juno principal investigator Scott Bolton, of the South-west Research Institute in San Antonio, Texas, said of the decision to leave the spacecraft in its current orbit. “The science will be just as spectacular as with our original plan.”

NASA Considering Crewed Option for Orion / SLS First Launch

NASA is considering making the first launch of its new Space Launch System (SLS) rocket, currently slated for September 2018, a crewed mission.

Under the agency’s existing plans, the first launch of the new rocket, topped by an Orion Multi-Purpose Crew Vehicle and dubbed Exploration Mission 1 (EM-1), would have seen SLS send an uncrewed Orion vehicle to the Moon and back, with around 6 days spent in lunar orbit. A crewed flight of the SLS / Orion combination would not take place until at least 2021, when crew would use Orion to rendezvous to a small asteroid previously captured via robotic means and moved to an extended orbit around the Moon – an idea which has garnered a certain amount of criticism from politicians.

An artist's impression of a Space Launch System / Orion combination lifting off from Kennedy Space Centre's Pad 39B. Credit: NASA

An artist’s impression of a Space Launch System / Orion combination lifting off from Kennedy Space Centre’s Pad 39B. Credit: NASA

If approved, the new proposal – put forward by NASA’s Acting Administrator, Robert Lightfoot – would see the planned EM-1 mission pushed back to 2018 (allowing the Orion vehicle to be outfitted with the crew lift support and flight systems) and flown with a crew of two. While this would mean a delay in the initial launch of SLS / Orion, it could ultimately accelerate NASA’s plans, allowing the agency to present a wider choice of crewed missions in the 2020s, and respond to criticism that it is not doing enough to demonstrate how it plans to achieve a return to the Moon and / or  missions to Mars.

Enceladus: Cradle for Life?

On February 17th, 2005 NASA’s Cassini space probe, part of the Cassini / Huygen mission, made its first flyby of Saturn’s moon Enceladus.

Scientists were naturally curious about the 500 km (360 mi) diameter moon, which is the most reflective object in the solar system, but assumed it was essentially a dead, airless world. However, Cassini immediately found this was not the case.

A dramatic plume sprays water ice and vapor from the south polar region of Saturn's moon Enceladus. Cassini's first hint of this plume came during the spacecraft's first close flyby of the icy moon on February 17, 2005. Credit: NASA/JPL / Space Science Institute

A dramatic plume sprays water ice and vapour from the south polar region of Saturn’s moon Enceladus. Cassini’s first hint of this plume came during the spacecraft’s first close flyby of the icy moon on February 17, 2005. Credit: NASA/JPL / Space Science Institute

The first thing that happened was the magnetometer on the spacecraft revealed that Saturn’s magnetic field, which envelops Enceladus, was perturbed above the moon’s south pole in a way that didn’t make sense for an inactive world – it was as if there was some interaction with an atmosphere.

In the second flyby, a month later, Cassini found the interaction seemed to suggest a plume of water vapour was rising from the moon. Then, in the third flyby, in July 2005, the probe imaged geysers of water vapour erupting from the moon’s south polar region, and thus Enceladus became the target of intense study. So much so, that while only those initial 3 flybys of the moon had been a part of the primary Cassini /Huygens mission profile, the mission was updated to allow 20 more flyby of the moon.

Today, we know that beneath the mantle of ice enclosing Enceladus there is an ocean of liquid water – the geysers are the results of that water breaking through this ice and jetting into space, giving rise to Saturn’s E-ring in the process. This ocean is likely to be warmed and kept liquid by hydrothermal vents on the sea floor, and these in turn – just like the vents theorised to be on the ocean floor of Jupiter’s Europa – might provide all the ingredients for basic life to arise.

To celebrate the 12th anniversary of Cassini’s discoveries with Enceladus, NASA has released a video documenting those initial findings from 2005.

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Space Sunday: Martian quandaries, universal epochs and Jovian journeys

"Yellowknife Bay" a region examined by the Curiosity Rover in 2012/13 indicated that a lake was once present in Gale Crater. However, the same rock has revealed that potentially, there was not sufficient carbon dioxide present in the atmosphere to help keep the water unfrozen

“Yellowknife Bay” a region examined by the Curiosity Rover in 2013 indicated that a lake was once present in Gale Crater. However, the same rock has revealed that potentially, there was not sufficient carbon dioxide present in the atmosphere to help keep the water unfrozen. Credit: NASA

Mars scientists are wrestling with a problem. Ample evidence says ancient Mars was sometimes wet, with water flowing and pooling on the planet’s surface. Yet, the ancient sun was about one-third less warm and climate modellers struggle to produce scenarios that get the surface of Mars warm enough for keeping water unfrozen.

A leading theory is that ancient Mars had a thicker carbon-dioxide atmosphere forming a greenhouse-gas blanket, helping to warm the surface. However an analysis of data from NASA’s Mars rover Curiosity, suggests that even 3.5 billion years ago there was too little carbon dioxide present in the Martian atmosphere to provide enough greenhouse-effect warming to prevent water freezing.

The source of these findings is the very same bedrock in which the rover found sediments from an ancient lake in which microbes might have thrived. When analysing the bedrock, Curiosity detected no carbonate minerals, leading to the conclusion that Mars’ atmosphere was almost devoid of carbon dioxide when the lake existed 3.5 billion years ago. And that’s a quandary for scientists.

Curiosity took this selfie while at "Yellowknife Bay" in 2013 whilst gathering rock samples for analysis. Note that while the shadow of the rover's robot arm can be assn, the arm itself is blanked from the images purely as a result of the angles used in individual shots and the way the images have been stitched together to provide a view of the rover

Curiosity took this selfie while at “Yellowknife Bay” in 2013 whilst gathering rock samples for analysis. Note that while the shadow of the rover’s robot arm can be seen, the arm itself is blanked from the images purely as a result of the angles used in individual shots and the way the images have been stitched together to provide a view of the rover. Credit: NASA

“We’ve been particularly struck with the absence of carbonate minerals in sedimentary rock the rover has examined,” Thomas Bristow, the principal investigator for Curiosity’s Chemistry and Mineralogy (CheMin) instrument,  the primary source of the analysis work. “It would be really hard to get liquid water even if there were a hundred times more carbon dioxide in the atmosphere than what the mineral evidence in the rock tells us.”

In water, carbon dioxide combines with positively charged ions such as magnesium and ferrous iron to form carbonate minerals, and CheMin can identify carbonate if it makes up just a few percent of the rock. Yet Curiosity has made no definitive detection of carbonates in any lakebed rocks sampled since it landed in Gale Crater in 2012. However, other minerals – magnetite and clay minerals – not only indicated in the same rocks indicate the ions needed to form carbonates were readily available, they also provide evidence that subsequent conditions never became so acidic that carbonates would have dissolved away over time.

The dilemma between a warm, wet Mars and the lack of carbonates has actually been growing for years. For two decades researchers have been using spectrometers on Mars orbiters to search for carbonate that could have resulted from an early era of more abundant carbon dioxide in the atmosphere, only to find far less than anticipated. Yet clues such as isotope ratios in today’s Martian atmosphere continue to indicate the planet once held a much denser atmosphere than it does now, which has largely been seen as being rich in carbon dioxide. Thus, a paradox has arisen.

Curiosity uses a spectrometer on its robot arm to check a rock dubbed "John Klein" in "Yellowknife Bay" for its suitability as a drilling target, January 25th, 2013. The drill itself can be seen on the robot arm's "hand", pointing up and to the right

Curiosity uses a spectrometer on its robot arm to check a rock dubbed “John Klein” in “Yellowknife Bay” for its suitability as a drilling target, January 25th, 2013. The drill itself can be seen on the robot arm’s rotating “hand”, pointing up and to the right. Credit: NASA

It had been thought that the lack of evidence for carbonates when seen from orbit could simply be the result of  dust covering them, or the carbonates having moved underground. Finding them would thus resolve the paradox and reveal what had happened. However, the Curiosity results tend to overturn this idea. Simply put, the rover has failed to detect carbonate minerals precisely where they should be located, within rocks formed from sediments deposited under water.

“This analysis fits with many theoretical studies that the surface of Mars, even that long ago, was not warm enough for water to be liquid,” said Robert Haberle, a Mars-climate scientist at NASA Ames. “It’s really a puzzle to me.”

One idea put forward is that perhaps the lake was never a body of open water, but was covered in ice. The problem with this idea is none of the expected evidence for an ice-covered lake, such as large and deep cracks called ice wedges, or “dropstones,” which become embedded in soft lakebed sediments when they penetrate thinning ice, have been found. Thus, scientists have a lot of head scratching and theorising to do in order to make sense of the dilemma.

Traversing Mars with Curiosity

A simulated Curiosity rolls over the "Naukluft Plateau" in this still from Seán Doran's video simulation of the rover's traverse

A simulated Curiosity rolls over the “Naukluft Plateau” in this still from Seán Doran’s video simulation of the rover’s traverse. Credit: Seán Doran.

Ever wondered what it would be like to witness Curiosity trundling across the surface of Mars? Seán Doran has. What’s more, he’s been putting together animated films using Digital Terrain Model (DTM) data from the HiRISE imaging system on NASA’s Mars Reconnaissance Orbiter together with photomosaics of images from the rover, and combining them with a drivable correctly scaled model of the rover to provide movies of Curiosity as it rolls across Mars.

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Space Sunday: remembrance and the future

Credit: NASA

The end of January / beginning of February is a time of pause and reflection for the American space programme and NASA. A span of five days, spread across a 36-year period, mark the three greatest tragedies of US human space flight, and so this period is always marked as a time of remembrance.

I’ve marked these three events – the Apollo 1 fire of January 27th, 1967, the Challenger disaster of January 28th, 1986 and the loss of the Columbia on February 1st, 2003 – in past Space Sunday updates. However, January 27th, 2017 marked the 50th anniversary of the Apollo 1 fire, which claimed the lives of Command Pilot Virgil I. “Gus” Grissom, Senior Pilot Edward H. White II, and Pilot Roger B. Chaffee in just 16 seconds. To mark it, and the start of NASA’s period of remembrance, the US space agency unveiled a new Apollo 1 tribute in its visitor complex at the Apollo/Saturn V Centre.

The Apollo 1 astronauts remembered at the Space Mirror Memorial, Kennedy SPace Centre's visitor centre

The Apollo 1 astronauts remembered at the Space Mirror Memorial, Kennedy Space Centre’s visitor centre. Credit: NASA

Grissom, White (the first American to walk in space during the Gemini 4 mission in 1965), and rookie Chaffee were participating in a “plugs out” test of the Apollo Command module intended to determine whether the vehicle was fit to fly at a time when many in NASA – Grissom included – felt it was not (Grissom had once famously hung a lemon in the Command Module simulator during training to signify his dissatisfaction with the state of the vehicle’s development).

It should have been a routine launch pad test of the vehicle the crew were due to fly in the first crewed test of Apollo in the run-up to a lunar landing. Instead, a spark from faulty wiring combusted the oxygen-rich atmosphere, causing a flash fire. This, aided by the many flammable materials used in the construction of the vehicle caused the air pressure inside the vehicle to rapidly rise, sealing the cabin’s inward opening hatch so that the crew could not open it themselves.

The deaths of these three men ultimately made Apollo – and the US space programme itself – far safer for those going into orbit. Flammable materials were all but eliminated from designs wherever possible; the atmosphere used within vehicles was altered so as not to be oxygen-rich, reducing the risk of fires rapidly building up and spreading; exit hatches were all changed so they would open outward, and the mechanisms for opening them either from within or without a vehicles were designed to be as simple and direct as possible.

To mark the 50th anniversary of the fire, NASA has placed the most significant part of the Apollo 1 vehicle – the hatch – on public display, with the full blessings of the surviving members of the astronaut’s families. It is a belated addition to similar exhibits of both the Challenger and Columbia accidents were placed on public display over 18 months ago in order to more fully commemorate those incidents.

All three disasters are commemorated at the Space Mirror Memorial  at the Kennedy Space Centre. However, while both Challenger and Columbia are also marked by memorials at America’s Arlington National Cemetery, no similar memorial currently exists for Apollo 1 (although Grissom and Caffee are interred there – White is interred at the West Point Cemetery). So, as a further mark of the 50th anniversary of the fire, Representative Eddie Bernice Johnson (D-Texas) has re-introduced a bill to Congress to have an Apollo 1 memorial established at Arlington.

The Challenger and Columbia memorials, Arlington National Cemetery

The Challenger and Columbia memorials, Arlington National Cemetery. Credit: Arlington National Cemetery.

Apollo 1, Challenger and Columbia, together with a loss of life which occurred during the Soviet manned space programme, serve as a reminder to all of us that space exploration is still a dangerous undertaking, despite all of the “shit sleeve” images we see of people working aboard the International Space Station. But then, all acts of expanding the human frontier carry with them inherent risks and the potential for loss of life.

This doesn’t mean we should shirk such activities or retreat from them; the rewards are simply too great, not only in terms of our potential to learn and grow and ensure our continuance as a species, but also to out ability to mature as a species and reach beyond the petty nationalisms and narrow-minded thinking which plague so much of what happens in the world today.

NASA’s official Day of Remembrance will be held on Tuesday, January 31st, 2017. With it comes the opportunity to not only look back to the sad events of January 27th, 2967, January 28th, 1986 and February 1st, 2003, but also to look forward to what might yet be achieved for all of human kind. Which is why I’m once again quoting Francis “Dick” Scobee, Commander of Challenger mission STS-51L, lost on that cold January morning in 1986.

Words: Francis Scobee via June Rodgers (formerly June Scobee). image: NASA

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