The Bering Strait is a sea passage that separates Russia and Alaska. It is usually covered with sea ice at this time of year – but as this image captured by the Copernicus Sentinel-1 mission on 7 March 2019 shows, it is virtually ice-free.
The Bering Strait is a narrow passage - around 80 km wide - connecting the Pacific and Arctic Oceans. The few patches of sea ice are shown in light-blue colours.
The extent of sea ice in the Bering Sea has dropped lower than it has been since written records began in 1850, and is most likely because of warm air and water temperatures. On average, the fluctuating sea ice in this region increases until early April, depending on wind and wave movement.
According to the National Snow & Ice Data Center, between 27 January to 3 March 2019, sea-ice extent decreased from 566 000 sq km to 193 000 sq km. Sea ice was also exceptionally low last year, but it has been reported that this March the extent of sea ice is the lowest in the 40-year satellite record.
To travel between Arctic and Pacific, marine traffic passes through the Bering Strait. Owing to the reduction of ice in the region, traffic has increased significantly.
The Copernicus Sentinel-1 satellites provide images to generate maps of sea-ice conditions for safe passage in the busy Arctic waters, as well as distinguish between thinner, more navigable first-year ice and thicker, more hazardous ice. Each satellite carries an advanced radar instrument to image Earth’s surface through cloud and rain, regardless of whether it is day or night.
This image captures a landform on Mars peculiar to the Hellas Basin, sometimes referred to as ‘banded terrain’. The pictured area belongs to the western part of the basin, which contains the lowest lying surfaces on Mars – up to 7 km below the defined zero level.
The terrain gives the impression that bands of material are flowing downhill. There is some evidence that the bands are ice-rich, but interpretations have not yet reached an agreement. In addition to the banded terrain seen at lower left and upper right in this orientation, some dust erosion in the form of dark streaks is also evident.
The image was taken by the Colour and Stereo Surface Imaging System (CaSSIS) onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter on 12 December 2018. It is centred at 39.04ºS/53.9ºE.
This remarkable image was taken in the Terra Sabaea region of Mars, west of Augakuh Vallis, by the Colour and Stereo Surface Imaging System (CaSSIS) onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter. This mysterious pattern sits on the crest of a ridge, and is thought to be the result of dust devil activity – essentially the convergence of hundreds or maybe even thousands of smaller martian tornadoes.
This image is a colour-composite representation where features that are bluer compared to the average colour of Mars are shown in bright blue hues. In actual colour, the streaks would appear dark red. Dust devils churn up the surface material, exposing fresher material below.
The reason why the streaks are so concentrated on the ridges is not known at present, but a relationship to orographic lift as masses of carbon dioxide air flow uphill and converge with other air masses is one possibility.
The image was taken on 8 February 2019 and is centred at 26.36ºN/56.96ºE. North is up.
This image covers a portion of the wall-terrace region of the 100 km-wide Columbus Crater located within Terra Sirenum in the southern hemisphere of Mars. The image was taken by the Colour and Stereo Surface Imaging System (CaSSIS) onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter on 15 January 2019.
Layered rocks that appear in light-tones are found extensively on the northern crater walls, terraces and floor. These rocks have subsequently been eroded to expose successive layers in cross-section.
The CRISM spectrometer onboard NASA’s Mars Reconnaissance Orbiter has already revealed that these layers contain various hydrated minerals, such as sulphate salts that appear to cover the white-coloured rocks. The beige-coloured layered rocks, consistent with a sulphate salt signature, appear to line the crater wall, reminiscent of a high water mark.
These ‘bathtub rings’ are consistent with deposits formed by lakes that start to dry up and, through evaporation, begin to deposit specific minerals turn by turn. As the water evaporates, the minerals that are the least readily dissolved in water will begin to precipitate out of the dwindling solution.
The relatively small 1.6 km-wide impact crater towards the top of the image appears to have a small amount of white-coloured bedrock exposed in its wall, which CRISM indicates is aluminous clay-bearing material. This suggests that the clay-bearing rocks are older than the sulphate salts that occupy the central portion of this image section.
Sites like these could have once offered conditions suitable for life.
The image is centred at 28.79ºS/193.84ºE. North is up.
Before Rosalind Franklin the ExoMars rover can search for signs of life on Mars, it must learn how to manoeuvre the landscape. Scientists and engineers are putting the rover through a series of locomotion tests to fine tune how it will respond to a challenging martian terrain.
The ExoMars mission will see Rosalind the rover and its surface platform land on Mars in 2021. There, the rover will move across many types of terrain, from fine-grained soil to large boulders and slopes to collect samples with a 2-m-long drill, and analyse them with instruments in its onboard laboratory. Engineers must ensure Rosalind does not get stuck in sand or topple over and that it is able to climb steep slopes and overcome rocks.
The ExoMars teams are using a dedicated rover to run locomotion tests. In this image, the full-sized locomotion model is about to move from the surface platform. This rover has been designed to behave exactly like Rosalind would do under martian gravity – that is about a third of gravity found on Earth. For that purpose, the model has a different weight distribution and features a boom mounted on top to achieve the exact location of the centre of gravity of the rover.
A special facility at RUAG Space in Zurich, Switzerland, emulates all the terrain conditions that Rosalind the rover is expected to encounter on Mars: different types of soil, various obstacle shapes and sizes and all kind of terrain slopes. A large hydraulic platform filled with 20 tonnes of soil was put in place for the tests.
Over the past few weeks, ESA, Roscosmos, Thales, Airbus and RUAG engineers have been testing the capability of the rover to egress from its landing platform onto the martian soil. Should the platform and rover find themselves on a slope upon landing, as simulated in the image, Rosalind the rover must be able to negotiate steep inclinations to descend from the platform. The team looked closely at the performance of the rover over the ramps at different inclination angles, from 5 up to 35 degrees.
The steep slope was a challenge for the rover. The wheels found it difficult at times to gain traction, a valuable lesson of what can be expected on Mars.
The rover has six wheels. Each wheel pair is suspended on a pivoted bogie so each wheel can be steered and driven independently. Its flexible metallic wheels, equipped with springs, offer great traction capability, allowing the rover to achieve better grip during obstacle climbing and achieve smoother locomotion.
Thanks to a triple-bogie locomotion system, the rover is able to overcome obstacles as big as its wheels. The rover uses inclinometers and gyroscopes to enhance its motion control.
Two cameras at the top of the rover’s mast allow Rosalind Franklin to see in 3D, like humans do, and identify rocks and slopes in front of it. This also allows the navigation system to take account of, and correct for, any wheel slippage. Rovers on Mars have previously been caught in sand, and continued wheel turning might actually dig them deeper – just like a car stuck in mud or snow.
These tests took place at the same time as the ExoFit field tests. In the most recent campaign, the rover drove from its landing platform and targeted sites of interest to sample rocks in the Mars-like landscapes of the Chilean desert.
A technician places a nearly 70 kg parachute designed for ESA and Roscosmos’s ExoMars 2020 mission inside the dry heater steriliser of the Agency’s Life, Physical Sciences and Life Support Laboratory, based in its Netherlands technical centre.
Mars is a potential abode of past and perhaps even present-day life. Accordingly, international planetary protection regulations require any mission sent to the Red Planet to undergo rigorous sterilisation, to prevent terrestrial microbes from piggybacking their way there.
The Lab’s Alan Dowson explains: “This is the ‘qualification model’ of the 35-m diameter main parachute for ExoMars 2020, basically a test version which allows us to finalise our sterilisation procedures ahead of the flight model chute’s arrival.
“This version has been threaded with thermal sensors, allowing us to see how long it takes to reach the required sterilisation temperature in all parts of the folded parachute, even in the hardest to heat points. Our target was to sterilise at 125 °C for 35 hours and 26 minutes, and the oven took about 44 hours to reach that temperature to begin with.”
The oven is part of the Lab’s 35 sq. m ‘ISO Class 1’ cleanroom, one of the cleanest places in Europe. All the cleanroom’s air passes through a two-stage filter system. Anyone entering the chamber has to gown up in a much more rigorous way than a hospital surgeon, before passing through an air shower to remove any remaining contaminants.
“If you imagine our clean room as being as big as the entire Earth’s atmosphere, then its allowable contamination would be equal to a single hot air balloon,” adds Alan. “Our ISO 1 rating means we have less than 10 dust particles measuring a tenth of one millionth of a metre in diameter per cubic metre of air.”
The mostly nylon and Kevlar parachute, packed into an 80-cm diameter donut-shaped unit, was delivered by Italy’s Arescosmo company. This qualification model will now be sent back there for testing, to ensure this sterilisation process causes no change to the parachute’s material properties.
Alan explains: “We will receive the parachute flight model later this spring for the same sterilisation process – identical to this version, except without any thermal sensors.”
ExoMars’s smaller first stage 15-m diameter parachute has already gone through sterilisation using the oven. This is the parachute that opens during initial, supersonic atmospheric entry, with the second, larger chute opening once the mission has been slowed to subsonic velocity.
The Lab has also tackled a variety of ExoMars instruments and subsystems, but this second stage subsonic parachute is the single largest item to be sterilised. The sterilisation process aims to reduce the overall mission ‘bioburden’ to a 10 thousandth of its original level.
The Copernicus Sentinel-2 mission takes us over Nairobi, one of the fastest growing cities in East Africa.
The population of Nairobi has increased significantly in the last 30 years, with rural residents flocking to the city in search of employment. The city, visible in the centre of the image, now has a population of over three million, with the vast majority spread over 200 informal settlements.
Kibera, which can be seen as a light-coloured patch at the south-western edge of the city, is considered one of the largest urban slums in Nairobi. Most residents live in small mud shacks with poor sanitation, a lack of electricity and limited access to clean water.
While migration provides economic benefits to the city, it also creates environmental challenges. Owing to its urbanisation, the city has spread into green spaces such as the nearby parks and forests. In this image, the densely populated area is contrasted with the flat plains of Nairobi National Park, directly south of the city. The 117 sq km of wide-open grass plains is coloured in light-brown. The park is home to lions, leopards, cheetahs and has a black rhino sanctuary.
The dark patches in the image are forests. The Ngong Forest, to the west of the city, includes exotic and indigenous trees, and hosts a variety of wild animals including wild pigs, porcupines, and dik-diks.
To the north of the city, the dark Karura Forest is visible. The 1000 hectare urban forest features a 15-m waterfall, and hosts a variety of animals including bush pigs, bushbucks, suni and harvey’s duiker, as well as some 200 bird species.
Although Africa is responsible for less than 5% of global greenhouse-gas emissions, the majority of the continent is directly impacted by climate change. Rapid population growth and urbanisation also exposes residents to climate risks.
On 14 March 2019, the first regional edition of the One Planet Summit took place at the UN Compound, which is in the north of the city. The One Planet Summit, part of the UN Environment Assembly, focuses on protecting biodiversity, promoting renewable energies and fostering resilience and adaptation to climate change.
Data from Copernicus Sentinel-2 can help monitor changes in urban expansion and land-cover change. Copernicus Sentinel-2 is a two-satellite mission. Each satellite carries a high-resolution camera that images Earth’s surface in 13 spectral bands.
This image, which was captured on 3 February 2019, is also featured on the Earth from Space video programme.
As delegates gather in Nairobi for the UN Environment Assembly, ESA is saddened by the news of the Ethiopian Airlines accident. Lives lost included those working for organisations also dedicated to achieving a better world for all and who were travelling to the assembly.
Our thoughts are with the families, colleagues and friends of those affected.
The copper-coloured baffle cover of our Characterising Exoplanet Satellite, Cheops, in the clean room at Airbus Defence and Space Spain, Madrid.
After completing spacecraft testing, the satellite has passed a very important review that determined it is ready to fly. Cheops will be stored in Madrid for a few months before being shipped to the launch site in Kourou, French Guiana; launch is scheduled in the time slot between 15 October and 14 November 2019.
The baffle cover pictured in this image is designed to protect the satellite’s scientific instrument – a powerful camera, or photometer – during assembly and launch. Once in space, the cover will open, allowing light from stars to enter the telescope.
Cheops will make observations of exoplanet-hosting stars to measure small changes in their brightness due to the transit of a planet across the star's disc, targeting in particular stars hosting planets in the Earth-to-Neptune size range. The information will enable precise measurements of the sizes of the orbiting planets to be made: combined with measurements of the planet masses, this will provide an estimate of their mean density – a first step to characterising planets outside our Solar System.
Cheops paves the way for the next generation of ESA’s exoplanet satellites, with two further missions – Plato and Ariel – planned for the next decade to tackle different aspects of the evolving field of exoplanet science.
More information: CHEOPS is ready for flight
Cracks cutting across Antarctica’s Brunt ice shelf are on course to truncate the shelf and release an iceberg about the size of Greater London. The Brunt ice shelf is an area of floating ice bordering the Coats Land coast in the Weddell Sea sector of Antarctica.
This Copernicus Sentinel-2 image from 7 February 2019 shows two lengthening fractures: a large chasm running northwards and a split, dubbed Halloween Crack, that has been extending eastwards since October 2016. They are now only separated by a few kilometres. Halloween Crack runs from an area known as McDonald Ice Rumples, which is where the underside of the otherwise floating ice sheet is grounded on the shallow seabed. This pinning point slows the flow of ice and crumples the ice surface into waves. Routine monitoring by satellites with different observing capabilities offer unprecedented views of events happening in remote regions like Antarctica, and how ice shelves manage to retain their structural integrity in response to changes in ice dynamics, air and ocean temperatures.
Read full story: Sentinels monitor converging ice cracks
In late 2018, ESA commissioned two consortia – one led by Airbus and the other by Thales Alenia Space – to undertake parallel studies into the design of a scientific airlock as part of a European module called ESPRIT. This module will enable refuelling, provide the interface for telecommunications with the Moon and Earth and allow scientific experiments to be transferred from the Gateway to and from outer space.
This image shows the underwater testing of one preliminary airlock design constructed by French company Comex for Airbus. The mock-up was tested underwater at Comex's facilities in Marseilles, France to simulate the weightlessness of space.
This Hubble Picture of the Week shows Messier 28, a globular cluster in the constellation of Sagittarius (The Archer), in jewel-bright detail. It is about 18 000 light-years away from Earth.
As its name suggests, this cluster belongs to the Messier catalogue of objects — however, when astronomer Charles Messier first added Messier 28 to his list in 1764, he catalogued it incorrectly, referring to it as a “[round] nebula containing no star”. While today we know nebulae to be vast, often glowing clouds of interstellar dust and ionised gases, until the early twentieth century a nebula represented any astronomical object that was not clearly localised and isolated. Any unidentified hazy light source could be called a nebula. In fact, all 110 of the astronomical objects identified by Messier were combined under the title of the Catalogue of Nebulae and Star Clusters. He classified many objects as diverse as star clusters and supernova remnants as nebulae. This includes Messier 28, pictured here — which, ironically, is actually a star cluster.
Messier’s mistake is understandable. Whilst Messier 28 is easily recognisable as a globular stellar cluster in this image, it is far less recognisable from Earth. Even with binoculars it is only visible very faintly, as the distorting effects of the Earth’s atmosphere reduce this luminous ancient cluster to a barely visible smudge in the sky. One would need larger telescopes to resolve single stars in Messier 28. Fortunately, from space Hubble allows Messier 28 to be seen in all its beauty — far more than a faint, shapeless, nebulous cloud.
Week in images
11 - 15 March 2019