Space Sunday: other worlds, near and far

Curiosity on “Mount Sharp” as seen by the Mars Reconnaissance Orbiter. Credit: NASA/JPL / MSSS  (click for full size)

NASA’s Mars Science Laboratory rover, Curiosity continues to climb Aeolis Mons (“Mount Sharp”), and in doing so, it has been once again imaged from orbit by the HiRISE camera system on NASA’s Mars Reconnaissance Orbiter (MRO). The image was captured on June 5th, 2017 (Curiosity’s 1717th Martian Sol), at the same time the rover was engaged in taking colour images of its surrounding using its mast-mounted Navcam system.

MRO has actually been imaging Curiosity roughly once every three months, as the orbiter’s track around Mars carries it over “Mount Sharp” and the rover’s route up the mound’s flank. However, these aren’t simply happy snaps of the rover’s progress: MRO is actively monitoring the terrain around the rover to allow scientists to check for changes – such as movement among sand dunes – and to help plan the rover’s route up the slopes.

The June 5th image, released by NASA on June 20th, has been colour enhanced to better reveal Curiosity as a bright blue feature. To give an idea of scale and resolution, the rover is some 3 metres (10ft) in length and 2.8 metres (9 ft) wide.

A mosaic of images captured by Curiosity using the Navcam system, looking back along the rover’ route up “Mount Sharp” towards the distant rim of Gale Crater. The images making up the view were all captured on June 5th, 2017 (Sol 1717 for the rover), the same day as MRO imaged the rover from orbit. Credit: see image

Curiosity is currently traversing ground between two points of scientific interest: the “Bagnold Dunes”, an area of sand dunes which are slowly progressing down the side of “Mount Sharp” as a result of both wind action and gravity; and a high-standing ridge which runs parallel to the eastward side of the dune field. Dubbed the “Vera Rubin Ridge” after the American astronomer who pioneered work on galaxy rotation rates, this ridge line is of interest to scientists because it has been shown to exhibit signatures of hematite, an oxidized iron mineral which can provide clues to the environmental conditions on this region of “Mount Sharp” when it formed.

The route to the ridge is slightly circuitous. At the moment the rover is heading east-north-east around a small set of dunes. Once clear of them it will turn south-east and drive to where a potential safe route up onto the ridge has been identified. The drive is further slowed as Curiosity periodically pauses to capture images of the feature to help scientists characterize any observed layers, fractures, or geologic contacts and better understand determine how the ridge formed, and its relationship to the other geologic units found within Gale Crater.

The route ahead: a June 14th (Sol 1726) mosaic captured by Curiosity, showing “Vera Rubin Ridge”, which was roughly 370 metres (114 ft) away from the rover at the time the images were captured. Credit: NASA/JPL / MSSS / Ken Kremer / Marco DiLorenzo

At the same time NASA released the image of Curiosity seen from orbit, half a world away, attempts to correct a wheel problem the solar-powered Opportunity Mars Exploration Rover (MER) had been experiencing appeared to end in partial success.

“Oppy” had suffered a failure with its left-front wheel steering actuator on June 4th, leaving the wheel angled and unable to straighten. After numerous attempts to correct the issue, a new approach tested on June 20th resulted in the wheel turning correctly and resuming its proper alignment with the other wheels. However, what originally caused the actuator to fail remains unknown, and there is concern that it might recur.

To limit the risk of this happening and possibly stranding “Oppy”, the rover will avoid all use of its front wheel steering, and will only use its rear wheel steering when absolutely necessary. To maintain manoeuvrability, it will instead rely on “tank steering” – effectively running the drive motors for the wheels on one side of the rover in opposition to those on the other, allowing Opportunity to turn left or right more-or-less on the spot, a technique the rover is designed to use. This should allow the rover to continue its current survey of “Perseverance Valley” in preparation for a descent into Endeavour Crater.

“Planet Nine” Set to Become “Planet Ten”?

I’ve written extensively in these pages about the hunt for “Planet Nine” (or “Planet X” or “George”, “Jehoshaphat” or “Planet of the Apes” as some would have it): the Neptune-sized world believed to be orbiting the sun at a distance of at least 200 astronomical units (AUs – one AU being the average distance of the Earth from the Sun) in a highly eccentric orbit.  The search for that world is still continuing, but if a new study is confirmed, that mystery world may well have to give up its “Planet Nine” title for another.

A planetary mass object the size of Mars would be sufficient to produce the observed perturbations in the distant Kuiper Belt. Credit: Heather Roper/LPL

Kat Volk and Renu Malhotra of the University of Arizona’s Lunar and Planetary Laboratory, offer compelling evidence of a yet-to-be-discovered planetary body with a mass somewhere between that of Mars and Earth, orbiting the Sun much closer than the mysterious “Planet Nine”, at around 50 AU distance.

Whilst carrying out a detailed studying of Kuiper Belt Objects (KBOs) – the disk of rocky asteroids and comets surrounding the Sun from a distance of around 30 AU to about 50-60 AU, Volk and Malhotra discovered a consistent anomaly. Whilst most KBOs surround the sun with orbital inclinations that average out to what planetary scientists call the “invariable plane of the solar system”, they discovered that the more distance KBOs – those around 50 AU or over from the Sun are tilted away from the invariable plane by about eight degrees.

The pair surveyed around 600 of the 2,000 observed KBOs, and found all of those on the outer reaches of the Kuiper Belt to be inclined from the invariable plane by roughly the same amount and in numbers that tend to preclude a statistical fluke. In modelling possible causes for this, they discovered that an object with a mass of Mars, orbiting about 50-60 AU would cause just such a disruption, as would a Earth-sized body slightly further away.

However, Volk and Malhotra carefully avoid any suggestion there is a Mars- or Earth-sized body is awaiting discovery, noting that the disruption might also be the result of several large (but not planet-sized) masses lying within the outer fringes of the Kuiper belt. Even so, a single body would seem more likely, and given it is effectively sitting within the galactic plane – an area so densely packed with stars that solar system surveys tend to avoid it – could explain why it has been able to remain undetected.

An artist’s rendering of the LSST atop Cerro Pachón mountain, Chile. When LSST starts taking images of the entire visible southern sky in 2022, it will produce the widest, deepest and fastest views of the night sky ever observed. Over a 10-year time frame, LSST will image several tens of billions of objects and create movies of the sky with unprecedented detail – and might reveal whatever is causing the odd perturbations among the KBOs studied by Volk and Malhotra. Credit: Large Synoptic Survey Telescope Project Office

But it might not remain hidden for much longer. 2020 should see the Large Synoptic Survey Telescope (LSST) come on-line. This 8.4 metre (27.6 ft) primary mirror telescope is due to commence a 10-year sky survey in 2022. Among other things, it is expected to increase the number of KBOs so far observed from 2000 – to over 40,000 as it carries out real-time surveys of the sky, night after night. In doing so, it could well find any planet-sized body lurking near them.

Continue reading “Space Sunday: other worlds, near and far”

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Space Sunday: Jupiter, exoplanets, Opportunity, and Wow! again

The planets – actual size. Jupiter is the biggest – and most likely the oldest – of our solar system’s family of gas and solid body planets. Credit: NASA

Jupiter is the most massive planet of the solar system and its presence had an immense effect on the dynamics of the solar accretion disk (the disk of dust and stellar material which surrounded and formed the Sun). Knowing the age of Jupiter is key for understanding how the solar system evolved toward its present-day architecture. Although models predict that Jupiter formed relatively early in the solar system’s history, until now, its formation has never been dated. Now, an international study suggests it was the very first planet to form.

The team, comprising scientists from the US Lawrence Livermore National Laboratory and Germany’s Institut für Planetologie at the University of Münster, believe that Jupiter’s core started forming within the first million years of the solar system’s existence. By looking at tungsten and molybdenum isotopes on iron meteorites, the team found that meteorites are made up from two genetically distinct nebular reservoirs that coexisted but remained separated between 1 million and 3-4 million years after the solar system formed.

“The most plausible mechanism for this efficient separation is the formation of Jupiter, opening a gap in the accretion disk, preventing the exchange of material between the two reservoirs,” said Thomas Kruijer, lead author of team’s paper, published in the June 12th Proceedings of the National Academy of Sciences.

“We do not have any samples from Jupiter (in contrast to other bodies like the Earth, Mars, the moon and asteroids),” he continued, when discussing the paper. “In our study, we use isotope signatures of meteorites (which are derived from asteroids) to infer Jupiter’s age. Jupiter is the oldest planet of the solar system, and its solid core formed well before the solar nebula gas dissipated, consistent with the core accretion model for giant planet formation.”

Even now, Jupiter sucks up material falling towards the Sun from further out in the solar system. This August 2009 image shows the result of an object striking the upper reaches of Jupiter’s southern hemisphere (south is at the top in the photo). The object was most likely a comet or asteroid a few hundred metres across. Credit: NASA

The team showed through isotope analyses of meteorites that Jupiter’s solid core formed within only about 1 million years after the start of the solar system history, rapidly growing to a mass of around 20 times that of Earth, then expanding more gradually to around 50 Earth masses over the next 2-3 million years. This rapid formation meant Jupiter acted as a barrier against inward transport of material from the outer reservoir of nebula material to the inner one, potentially explaining why our solar system lacks any super-Earths (a solid planet with a mass and size greater than Earth’s) orbiting the sun – Jupiter effectively vacuumed up the material.

The common belief among planetary scientists has leaned towards the gas giants of the outer solar system having formed relatively early in the solar system’s history, before the complete dissipation of the solar nebula—the gaseous circumstellar disk surrounding the young Sun – which occurred around 10 million years after the solar system formed. These finding fully support that belief, but has been able to far more precisely pin-down Jupiter’s birth date.

“Our measurements show that the growth of Jupiter can be dated using the distinct genetic heritage and formation times of meteorites,” Kruijer said.

Chinese Resupply Vehicle Competes 2nd Lab Refuelling

China’s automated Tianzhou-1 re-supply vehicle has carried out a successful second rendezvous with the currently uncrewed  Tiangong-2 space laboratory, and completed out a further refuelling operation of the orbital facility.

An artist’s impression of Tianzhou-1 (left) docked with the slightly larger Tiangong-2 orbital laboratory. Credit: CMSE

Launched in April 2017, Tianzhou-1 (“Heavenly Ship 1”) is the first of a series of resupply vehicles based on China’s first orbital module, Tiangong-1, designed to deliver up to 6.5 tonnes of equipment, supplies and fuel to orbital facilities – most notably China’s space station, construction of which is due to commence in 2018.

The 10.6m (34ft) long, 13 tonne Tianzhou-1 being prepared for installation into its launch shroud, April 2017. Image: CCTV

Tianzhou-1 is currently on an extended mission with the Tiangong-2 (“Heavenly Palace 2”) orbital facility, during which automated dockings at each of the laboratory’s two airlock systems are being practised, as is the transfer of fuel to the laboratory. The latter is a complicated, 29-step process, but one vital to the success of an orbital facility, where fuel is used in very small motor systems to help it maintain the correct orientation whilst in orbit and – potentially – help periodically boost the facility orbit to counter the microscopic (but cumulative) effect of atmospheric drag encountered whilst orbiting the Earth.

However, as such “boosts” to a space station’s orbit are more normally provided by an attached vehicle (the space shuttle used to do it for the International Space Station, for example, and the role has been taken over by the resupply craft which periodically visit the ISS). To this end, part of the Tianzhou-1 mission has also been to practice manoeuvring both the vehicle and  Tiangong-2 when the two have been docked. In addition, Tianzhou-1 has been carrying out its own free flight mission when not docked with the laboratory.

Like the European Automated Transfer Vehicle (ATV), Japanese H-II Transfer Vehicle (HTV) and American Cygnus resupply craft used in support of ISS operations, Tianzhou-1 is not designed to return to Earth. Instead, the vehicle will be allowed to burn-up as it re-enters the denser part of the Earth’s atmosphere at the end of its mission.

Following the Tianzhou-1 mission, a further crew of Chinese tiakonauts is expected to visit Tiangong-2 laboratory.

Kepler’s Latest Findings

NASA will announce the latest crop of planet discoveries from the Kepler Space Telescope on Monday, June 19th.

An artistic concept demonstrating gravitational microlensing. As an exoplanet passes in front of a more distant star, its gravity causes the trajectory of the starlight to bend, and in some cases results in a brief brightening of the background star as seen by a telescope, enabling scientists to search for exoplanets that are too distant and dark to be detected any other way (Credit: NASA / JPL / T. Pyle)

Kepler has been hunting for extrasolar planets since its launch in 2009, although the programme was almost cut short in 2013, following the failure of two of the reaction wheels (essentially gyroscope systems) used to stabilise the platform and allow it to gather data.

However, in November 2013, a new mission for the platform, dubbed “Second Light” and more generally referred to as the K2 mission,  was proposed and, after a successful period of test in early 2014, officially got under way on May 26th, 2014.

Most recently, Kepler has been using gravitational microlensing in an attempt to locate planets  orbiting stars so far away, the dimming of the star’s light by a transiting planet cannot easily be detected.

Kepler was the first mission capable of seeing planets the size of Earth around other stars in the “habitable zone” — the region at a distance from a star where liquid water could exist without freezing or boiling away immediately.

Thus far Kepler has found 4,496 exoplanet candidates. Some 2,335 have been confirmed and 21 are Earth-size planets in the habitable zone. Further, 520 of these exoplanet candidates have been found during the K2 mission, with 148 confirmed as having planets.

Continue reading “Space Sunday: Jupiter, exoplanets, Opportunity, and Wow! again”

Space Sunday: more Einstein, plus space planes and Wow!

This illustration reveals how the gravity of a white dwarf star warps space and bends the light of a distant star behind it. Credit: NASA, ESA, and A. Feild (STScI)

In his general theory of relativity, Albert Einstein predicted that whenever light from a distant star passes by a closer object, gravity acts as a kind of magnifying lens, brightening and bending the distant starlight in an effect known as “gravitational microlensing”.  While such microlensing has been observed using the Sun, it has never been used against an individual star (although it has been used binary pairs of stars) – until now.

During a two-year period between October 2013 and October 2015, astronomers used the Hubble Space Telescope (HST) did just that, allowing them to measure the mass of a star in the process.

The star in question is a white dwarf called Stein 2051 B, roughly 18 light years from Earth and part of a binary system, paired with a red dwarf. Essentially, the team of astronomers used Hubble to observe the effect the white dwarf had on the light being received from a star 5,000 light years away. By measuring the amount of apparent light deflection, the team were not only able to further confirm Einstein’s theory of relativity – they were able to measure the mass of the white dwarf itself, even though the deflection was tiny – only 2 milliarcseconds from its actual position.

“This microlensing method is a very independent and direct way to determine the mass of a star,” Kailash Sahu, the lead researcher on the project, explained following the publication of his team’s findings on June 7th, 2017. “It’s like placing the star on a scale: the deflection is analogous to the movement of the needle on the scale.”

On top of this, the observations confirmed the theory that a white dwarf star’s size is determined by its mass, first postulated in 1935 by Subrahmanyan Chandrasekhar, the Indian-American astronomer. Thus, a single set of observations have further confirmed Einstein’s theory of space-time to be correct (and sits alongside the detection of gravitational waves – see my last Space Sunday update – and observations of rapidly spinning pulsars in doing so), and confirmed the defining limits for a white dwarf star and allowed astronomers effectively measure the mass of a star.

Space Plane News

The United States Air Force has confirmed that the next mission for its X37B automated space plane will utilise a SpaceX Falcon 9 launch vehicle to boost it into orbit in August 2017.  This will be the fifth launch of the X-37B, which is also known as the Orbital Test Vehicle, and the first time a United Launch Alliance Atlas V booster hasn’t been used. It also marks the highest-profile US national security launch SpaceX will have signed-up for.

There are actually two of the uncrewed X-37B vehicles operated by the USAF which have been flown on alternate missions. The second of these two craft returned to Earth in May 2017 after spending an astonishing 718 days in orbit, carrying a mixed classified and non-classified cargo. The August mission will likely use the first of the two vehicles in its third mission, and will feature the Air Force Research Laboratory (AFRL) Advanced Structurally Embedded Thermal Spreader (ASETS-11) to test experimental electronics and oscillating heat pipes in the long duration space environment.

The USAF’s X-37B Orbital Test Vehicle (OTV) on the runway at Kennedy Space Centre at the end of the programme’s fourth mission, May 7th, 2017. The uncrewed vehicle is being “safed” by a Boeing team in protective suits to guard against harmful fumes and gases given off by the vehicle. Credit: USAF

At the same time as the USAF announcement about the X-37B, the South China Morning Post reported China’s own space plane programme is making “significant progress”.

China has been investigating the potential of operating some form of space plane since the late 1980s. Those plans ultimately didn’t go anywhere, and rumours of a new Chinese space plane, capable of flying astronauts and / or cargo to low Earth orbit started circulating in 2016, thanks to a news broadcast on Chinese state television service CCTV. However, as the report used imagery clearly taken from the UK’s Skylon programme, there was some doubt as to the veracity of the report.

 

In “announcing” the new space plane in 2016, China State television used images of the UK’s Skylon programme. Credit: CCTV

Like Skylon, the new Chinese vehicle, which the South China Morning Post refers to as athe Casic (the initials of the China Aerospace Science and Industry Corporation, said to be building the vehicle), will be able to take-off horizontally and use a hybrid propulsion system capable of flying it through the atmosphere and into space, carrying a crew and / or cargo to low Earth orbit. At the end of a mission, the vehicle will return to Earth and land on a conventional runway, where it can be re-serviced pretty much like a conventional military aircraft.

The South China Morning Post indicates that the new vehicle has “finished almost all ground experiments and overcome key technical hurdles such as engine design and construction”. However, no dates on when the vehicle might be rolled-out or start flight tests have been given. Nor have any specifics or official images of the vehicle been released. All that has been said is the vehicle will have an “aerodynamic shape” for atmospheric flight, and be larger than Virgin Galactic’s SpaceShipTwo, the VSS Unity.

Continue reading “Space Sunday: more Einstein, plus space planes and Wow!”

Space Sunday: Wet Mars, Einstein, Jupiter, and monster launchers

Curiosity, NASA’s Mars Science Laboratory rover, has found further evidence that Gale Crater had liquid water present within it for a long time, and the data the rover has gathered during its explorations is allowing scientists to better characterise the nature of the lake which once occupied the crater.

In 2015 Curiosity encountered pale “halos” around fractures the bedrock on the lower slopes of “Mount Sharp”. Analysis of spectrographic data gathered by the rover’s on-board Chemistry and Camera (ChemCam) instrument has confirmed they contain copious silica. This indicates the crater held liquid water for a long time in aeons past.

“The concentration of silica is very high at the centre lines of these halos,” said Jens Frydenvang, a rover-team scientist at Los Alamos National Laboratory in New Mexico, and the University of Copenhagen in Denmark. “What we’re seeing is that silica appears to have migrated between very old sedimentary bedrock and into younger overlying rocks. These  findings tells us is that, even when the lake eventually evaporated, substantial amounts of groundwater were present for longer than we previously thought — further expanding the window for when life might have existed on Mars.””

Pale zones called “halos” border bedrock fractures visible in this 2015 image from Curiosity, captured on the lower slopes of “Mount Sharp”. The overlay indicates the scale for the size of these fractures. The halos have been shown to be rich in silica, a clue to the duration of wet environmental conditions in the crater long ago. Credit: NASA/JPL / MSSS

Further to this, a new study reveals that the ancient lake in Gale Crater likely provided stable environmental conditions that differed significantly from one part of to another, potentially allowing different types of microbes to exist at different points simultaneously in the same lake, the water within it being stratified in a similar manner to water in lakes on Earth. In Gale Crater’s case, the shallow water was richer in oxidants than deeper water was.

The study combines the analyses of the chemical and mineral composition of rocks found at different points along Curiosity’s ascent up mount sharp reveal a clear correspondence between the physical characteristics of sedimentary rock from different parts of the lake, and how strongly oxidised they were. In essence, those rocks with the physical characteristics of having been deposited near the edge of the lake have a stronger oxidised composition than those with physical characteristics indicative of being deposited in deeper water.

The sedimentary rocks deposited within a lake in Mars’ Gale Crater more than three billion years ago differ from each other in a pattern that matches what is seen in lakes on Earth. As sediment-bearing water flows into a lake, bedding thickness and particle size progressively decrease as sediment is deposited in deeper and deeper water. Credit: NASA/JPL / Stony Brook University

“These were very different, co-existing environments in the same lake,” said Joel Hurowitz of Stony Brook University, Stony Brook, New York, lead author of the study. “The diversity of environments in this Martian lake would have provided multiple opportunities for different types of microbes to survive, including those that thrive in oxidant-rich conditions, those that thrive in oxidant-poor conditions, and those that inhabit the interface between.”

This doesn’t mean that there were microbes swimming around in the waters of Gale Crater, but it does offer a further indication that the lake was a potentially benign environment for such microbes, if life on Mars ever developed that far.

In addition, the study offers further insights to the overall environmental changes which occurred on Mars, suggesting that while across the aeons, things went from warm and wet to cold and arid, Gale Crater exhibited short-term fluctuations in the other direction, at times becoming warmer and wetter. Findings which correspond to earlier studies suggesting the sediments comprising “Mount Sharp” were laid down as a result of several different wet periods in the crater’s history.

LIGO Records Third Gravitational Wave Event

In February 2016, I wrote about LIGO – the Large Interferometer Gravitational Wave Observatory – an international quest established in 1992 to detect gravitational waves. At that time, it had just been confirmed that, quiet unexpectedly, two brand-new LIGO detectors in the United States had almost simultaneously recorded gravitational waves as they came out of “engineering mode” tests and were being run up to full operational mode, in September 2015.

The LIGO observatory, Hanford, Washington State

It was later confirmed that the two detectors, funded National Science Foundation and located in Livingston, Louisiana, and Hanford, Washington State, had made a further detection of gravitational waves in December 2015. On June 2nd, 2017, it was confirmed the instruments at Livingston and Hanford had detected gravitational waves for a thirdtime in January 2017.

Predicted over a century ago by Einstein in his theory of general relativity, gravitational waves (not to be confused with “gravity waves”, which are something else entirely) are at their most basic, ripples in space-time, generated by the acceleration or deceleration of massive objects in the cosmos. So, for example, if a star goes supernova or two black holes collide or if two super-massive neutron stars orbit closely about one another, they will distort space-time, creating ripples which propagate outwards from their source, like ripples across the surface of a pond. As such, their detection goes a long way to confirming Einstein’s description of space-time as an integrated continuum.

In all three of the case so far detected, the gravitational waves have been traced to the merger of black holes. In the case on the latest detection – called GW170104 after the date of its detection – the two black holes are roughly three billion light years away from Earth, twice the distance of the first two detections.

That all three events have been the result of the merger of black holes suggests that binary black hole systems are potentially far more common than had been believed, and mergers between them could be occurring a lot faster than previously predicted. They are, however, an ideal target for gravitational wave detection: when they do merge they can produce more power than is radiated as light by all the stars and galaxies in the universe at any given time.

An international team of researchers has made a third detection of gravitational waves, ripples in space and time, in a discovery that provides new insights into the mysterious nature of black holes and, potentially, dark matter. Credit: LSC / OzGrav

Having three sources for gravitational waves now means that scientists can now analyse them in detail. The two already discovered have not only confirmed Einstein’s prediction that such phenomena would exist, but also that the waves themselves do not suffer from dispersion – again as Einstein predicted would be the case. the readings from GW170104 further indicate no dispersion is apparent in the waves, even across 3 billion light years of propagation from their source.

As well as helping confirm Einstein’s model of space-time, LIGO’s studies of these black holes will allow for a more detailed examination of the nature and properties of black holes themselves, presenting a treasure trove of understanding for science. Currently, LIGO is mid-way through its third run of observations of deep space, which will end in late summer. Thereafter the facilities at Livingston and Hanford will undergo a period of upgrade and testing, before a fourth round of observations commence in 2018.

Continue reading “Space Sunday: Wet Mars, Einstein, Jupiter, and monster launchers”