Space and astronomy news
Even though Earthling scientists are studying Mars intently, it’s still a mysterious place.
One of the striking things about Mars is all of the evidence, clearly visible on its surface, that it harbored liquid water. Now, all that water is gone, and in fact, liquid water couldn’t survive on the surface of the Red Planet. Not as the planet is now, anyway.
But it could harbour water in the past. What happened?
Continue reading “Mars Doesn’t Have Much of a Magnetosphere, But Here’s a Map”
Every second of every day, our sun spits out a stream of tiny high-energy particles, known as the solar wind. This wind blows throughout the solar system, extending far beyond the orbits of the planets and out into interstellar space.
But the farther from the sun the wind gets, the more slowly it streams, changing from the raging torrent that the inner planets experience (strong enough to cause the aurora) into nothing more than an annoying drizzle. And far enough away – about twice the orbit of Neptune – it meets and mingles with all the random bits of energetic junk just floating around amongst the stars.
Continue reading “The heliosphere looks a lot weirder than we originally thought”
On February 10th, 2020, the ESA’s Solar Orbiter (SolO) launched and began making its way towards our Sun. This mission will spend the next seven years investigating the Sun’s uncharted polar regions to learn more about how the Sun works. This information is expected to reveal things that will help astronomers better predict changes in solar activity and “space weather”.
Last week (on Thursday, Feb. 13th), after a challenging post-launch period, the first solar measurements obtained by the SolO mission reached its international science teams back on Earth. This receipt of this data confirmed that the orbiter’s instrument boom deployed successfully shortly after launch and that its magnetometer (a crucial instrument for this mission) is in fine working order.
Continue reading “Solar Orbiter is Already Starting to Observe the Sun”
The Sun is not exactly placid, though it appears pretty peaceful in the quick glances we can steal with our naked eyes. In reality though, the Sun is a dynamic, chaotic body, spraying out solar wind and radiation and erupting in great sheets of plasma. Living in a technological society next to all that is a challenge.
Continue reading “ESA is Considering a Mission to Give Advanced Warnings of Solar Storms”
In the coming years, a number of will be sent to space for the purpose of answering some of the enduring questions about the cosmos. One of the most pressing is the effect that solar activity and “space weather” events have on planet Earth. By being able to better-predict these, scientists will be able to create better early-warning systems that could prevent damage to Earth’s electrical infrastructure.
This is the purpose of the Solar Orbiter (SolO), an ESA-led mission with strong participation by NASA that launched this morning (Monday, Feb. 10th) from Cape Canaveral, Florida. This is the first “medium-class” mission implemented as part of the ESA’s Cosmic Vision 2015-25 program and will spend the next five years investigating the Sun’s uncharted polar regions to learn more about how the Sun works.
Continue reading “The ESA’s Solar Orbiter, a Mission That Will Chart the Unexplored Polar Regions of the Sun, Just Launched!”
Earth’s fleet of satellites is in a vulnerable position. When solar activity increases, high-energy particles are directed toward Earth. Our large fleet is in the direct path of all that energy, which can damage them or render them inoperable. But now we have another tool to help us protect our satellites.
Continue reading “Space Weather Forecasts can now give Satellites One Whole Day of Warning when a Killer Solar Storm is Inbound”
In 2014 , the European Space Agency’s (ESA) Rosetta spacecraft made history when it rendezvoused with Comet 67P/Churyumov-Gerasimenko. This mission would be the first of its kind, where a spacecraft intercepted a comet, followed it as it orbited the Sun, and deployed a lander to its surface. For the next two years, the orbiter would study this comet in the hopes of revealing things about the history of the Solar System.
In this time, Rosetta’s science team also directed the orbiter to look for signs of the comet’s bow shock – the boundary that forms around objects as a result of interaction with solar wind. Contrary to what they thought, a recent study has revealed that Rosetta managed to detect signs of a bow shock around the comet in its early stages. This constitutes the first time in history that the formation of a bow shock has been witnessed in our Solar System. Continue reading “Rosetta Flew Through the Bow Shock of Comet 67P Several Times During its Mission”
When it comes to exploring our Solar System, there are few missions more ambitious than those that seek to study the Sun. While NASA and other space agencies have been observing the Sun for decades, the majority of these missions were conducted in orbit around Earth. To date, the closest any mission has ever come to the Sun was with the Helios 1 and 2 probes, which studied the Sun during the 1970s from inside of Mercury’s orbit at perihelion.
NASA intends to change all that with the Parker Solar Probe, the space probe that recently launched from Cape Canaveral, which will revolutionize our understanding of the Sun by entering its atmosphere (aka. the corona). Over the next seven years, the probe will use Venus’ gravity to conduct a series of slingshots that will gradually bring it closer to the Sun than any mission in the history of spaceflight!
Continue reading “The Sun is Actually One of the Most Difficult Places to Reach in the Solar System. Here’s how the Parker Solar Probe Will Do It”
To the naked eye, the Sun puts out energy in a continual, steady state, unchanged through human history. (Don’t look at the sun with your naked eye!) But telescopes tuned to different parts of the electromagnetic spectrum reveal the Sun’s true nature: A shifting, dynamic ball of plasma with a turbulent life. And that dynamic, magnetic turbulence creates space weather.
Space weather is mostly invisible to us, but the part we can see is one of nature’s most stunning displays, the auroras. The aurora’s are triggered when energetic material from the Sun slams into the Earth’s magnetic field. The result is the shimmering, shifting bands of color seen at northern and southern latitudes, also known as the northern and southern lights.
There are two things that can cause auroras, but both start with the Sun. The first involves solar flares. Highly-active regions on the Sun’s surface produce more solar flares, which are sudden, localized increase in the Sun’s brightness. Often, but not always, a solar flare is coupled with a coronal mass ejection (CME).
A coronal mass ejection is a discharge of matter and electromagnetic radiation into space. This magnetized plasma is mostly protons and electrons. The CME ejection often just disperses into space, but not always. If it’s aimed in the direction of the Earth, chances are we get increased auroral activity.
The second cause of auroras are coronal holes on the Sun’s surface. A coronal hole is a region on the surface of the Sun that is cooler and less dense than surrounding areas. Coronal holes are the source of fast-moving streams of material from the Sun.
Whether it’s from an active region on the Sun full of solar flares, or whether it’s from a coronal hole, the result is the same. When the discharge from the Sun strikes the charged particles in our own magnetosphere with enough force, both can be forced into our upper atmosphere. As they reach the atmosphere, they give up their energy. This causes constituents in our atmosphere to emit light. Anyone who has witnessed an aurora knows just how striking that light can be. The shifting and shimmering patterns of light are mesmerizing.
The auroras occur in a region called the auroral oval, which is biased towards the night side of the Earth. This oval is expanded by stronger solar emissions. So when we watch the surface of the Sun for increased activity, we can often predict brighter auroras which will be more visible in southern latitudes, due to the expansion of the auroral oval.
Something happening on the surface of the Sun in the last couple days could signal increased auroras on Earth, tonight and tomorrow (March 28th, 29th). A feature called a trans-equatorial coronal hole is facing Earth, which could mean that a strong solar wind is about to hit us. If it does, look north or south at night, depending on where your live, to see the auroras.
Of course, auroras are only one aspect of space weather. They’re like rainbows, because they’re very pretty, and they’re harmless. But space weather can be much more powerful, and can produce much greater effects than mere auroras. That’s why there’s a growing effort to be able to predict space weather by watching the Sun.
A powerful enough solar storm can produce a CME strong enough to damage things like power systems, navigation systems, communications systems, and satellites. The Carrington Event in 1859 was one such event. It produced one of the largest solar storms on record.
That storm occurred on September 1st and 2nd, 1859. It was preceded by an increase in sun spots, and the flare that accompanied the CME was observed by astronomers. The auroras caused by this storm were seen as far south as the Caribbean.
The same storm today, in our modern technological world, would wreak havoc. In 2012, we almost found out exactly how damaging a storm of that magnitude could be. A pair of CMEs as powerful as the Carrington Event came barreling towards Earth, but narrowly missed us.
We’ve learned a lot about the Sun and solar storms since 1859. We now know that the Sun’s activity is cyclical. Every 11 years, the Sun goes through its cycle, from solar maximum to solar minimum. The maximum and minimum correspond to periods of maximum sunspot activity and minimum sunspot activity. The 11 year cycle goes from minimum to minimum. When the Sun’s activity is at its minimum in the cycle, most CMEs come from coronal holes.
NASA’s Solar Dynamics Observatory (SDO), and the combined ESA/NASA Solar and Heliospheric Observatory (SOHO) are space observatories tasked with studying the Sun. The SDO focuses on the Sun and its magnetic field, and how changes influence life on Earth and our technological systems. SOHO studies the structure and behavior of the solar interior, and also how the solar wind is produced.
Several different websites allow anyone to check in on the behavior of the Sun, and to see what space weather might be coming our way. The NOAA’s Space Weather Prediction Center has an array of data and visualizations to help understand what’s going on with the Sun. Scroll down to the Aurora forecast to watch a visualization of expected auroral activity.
NASA’s Space Weather site contains all kinds of news about NASA missions and discoveries around space weather. SpaceWeatherLive.com is a volunteer run site that provides real-time info on space weather. You can even sign up to receive alerts for upcoming auroras and other solar activity.
Every planet in our Solar System interacts with the stream of energetic particles coming from our Sun. Often referred to as “solar wind”, these particles consist mainly of electrons, protons and alpha particles that are constantly making their way towards interstellar space. Where this stream comes into contact with a planet’s magnetosphere or atmosphere, it forms a region around them known as a “bow shock”.
These regions form in front of the planet, slowing and diverting solar wind as it moves past – much like how water is diverted around a boat. In the case of Mars, it is the planet’s ionosphere that provides the conductive environment necessary for a bow shock to form. And according to a new study by a team of European scientists, Mars’ bow shock shifts as a result of changes in the planet’s atmosphere.
The study, titled “Annual Variations in the Martian Bow Shock Location as Observed by the Mars Express Mission“, appeared in the Journal of Geophysical Letters: Space Physics. Using data from the Mars Express orbiter, the science team sought to investigate how and why the bow shock’s location varies during the course of several Martian years, and what factors are chiefly be responsible.
For many decades, astronomers have been aware that bow shocks form upstream of a planet, where interaction between solar wind and the planet causes energetic particles to slow down and gradually be diverted. Where the solar wind meets the planet’s magnetosphere or atmosphere, a sharp boundary line is formed, which them extends around the planet in a widening arc.
This is where the term bow shock comes from, owing to its distinctive shape. In the case of Mars, which does not have a global magnetic field and a rather thin atmosphere to boot (less than 1% of Earth’s atmospheric pressure at sea level), it is the electrically-charged region of the upper atmosphere (the ionosphere) that is responsible for creating the bow shock around the planet.
At the same time, Mars relatively small size, mass and gravity allows for the formation of an extended atmosphere (i.e. an exosphere). In this portion of Mars’ atmosphere, gaseous atoms and molecules escape into space and interact directly with solar wind. Over the years, this extended atmosphere and Mars’ bow shock have been observed by multiple orbiter missions, which have detected variations in the latter’s boundary.
This is believed to be caused by multiple factors, not the least of which is distance. Because Mars has an relatively eccentric orbit (0.0934 compared to Earth’s 0.0167), its distance from the Sun varies quite a bit – going from 206.7 million km (128.437 million mi; 1.3814 AU) at perihelion to 249.2 million km (154.8457 million mi; 1.666 AU) at aphelion.
When the planet is closer, the dynamic pressure of the solar wind against its atmosphere increases. However, this change in distance also coincides with increases in the amount of incoming extreme ultraviolet (EUV) solar radiation. As a result, the rate at which ions and electrons (aka. plasma) are produced in the upper atmosphere increases, causing increased thermal pressure that counteracts the incoming solar wind.
Newly-created ions within the extended atmosphere are also picked up and accelerated by the electromagnetic fields being carried by the solar wind. This has the effect of slowing it down and causing Mars’ bowshock to shift its position. All of this has been known to happen over the course of a single Martian year – which is equivalent to 686.971 Earth days or 668.5991 Martian days (sols).
However, how it behaves over longer periods of time is a question that was previously unanswered. As such, the team of European scientists consulted data obtained by the Mars Express mission over a five year period. This data was taken by the Analyser of Space Plasma and EneRgetic Atoms (ASPERA-3) Electron Spectrometer (ELS), which the team used to examine a total of 11,861 bow shock crossings.
What they found was that, on average, the bow shock is closer to Mars when it is near aphelion (8102 km), and further away at perihelion (8984 km). This works out to a variation of about 11% during the Martian year, which is pretty consistent with its eccentricity. However, the team wanted to see which (if any) of the previously-studied mechanisms was chiefly responsible for this change.
Towards this end, the team considered variations in solar wind density, the strength of the interplanetary magnetic field, and solar irradiation as primary causes – are all of which decline as the planet gets farther away from the Sun. However, what they found was that the bow shock’s location appeared more sensitive to variations in the Sun’s output of extreme UV radiation rather than to variations in solar wind itself.
The variations in bow shock distance also appeared to be related to the amount of dust in the Martian atmosphere. This increases as Mars approaches perihelion, causing the atmosphere to absorb more solar radiation and heat up. Much like how increased levels of EUV leads to an increased amount of plasma in the ionosphere and exosphere, increased amounts of dust appear to act as a buffer against solar wind.
As Benjamin Hall, a researcher at Lancaster University in the UK and the lead author of the paper, said in an ESA press release:
“Dust storms have been previously shown to interact with the upper atmosphere and ionosphere of Mars, so there may be an indirect coupling between the dust storms and bow shock location… However, we do not draw any further conclusions on how the dust storms could directly impact the location of the Martian bow shock and leave such an investigation to a future study.”
In the end, Hall and his team could not single out any one factor when addressing why Mars’ bow shock shifts over longer periods of time. “It seems likely that no single mechanism can explain our observations, but rather a combined effect of all of them,” he said. “At this point none of them can be excluded.”
Looking ahead, Hall and his colleagues hope that future missions will help shed additional light on the mechanisms behind Mars shifting bowshock. As Hall indicated, this will likely involve “”joint investigations by ESA’s Mars Express and Trace Gas Orbiter, and NASA’s MAVEN mission. Early data from MAVEN seems to confirm the trends that we discovered.”
While this is not the first analysis that sought to understand how Mars’ atmosphere interacts with solar wind, this particular analysis was based on data obtained over a much longer period of time than any previously study. In the end, the multiple missions that are currently studying Mars are revealing much about the atmospheric dynamics of this planet. A planet which, unlike Earth, has a very weak magnetic field.
What we learn in the process will go a long way towards ensuring that future exploration missions to Mars and other planets that have weak magnetic fields (like Venus and Mercury) are safe and effective. It might even assist us with the creation of permanent bases on these worlds someday!
Further Reading: ESA, Journal of Geophysical Research: Space Physics