It’s a busy February for Mars, with three probes from three separate countries arriving at the Red Planet over the course of just nine days. But this Martian party didn’t happen by coincidence — it has to do with the mechanics of both Earth and Mars’ orbits.
The United Arab Emirates’ first interplanetary mission, the Hope probe, achieved Mars orbit Tuesday (Feb. 9), as Live Science sister site Space.com reported. China’s first interplanetary mission, Tianwen-1, is scheduled to enter its own Martian orbit Wednesday (Feb. 10). The Chinese probe includes both an orbiter and a lander with a rover onboard, which is expected to try to land on the surface in May. And on Feb. 18, NASA’s first-of-its-kind descent vehicle will reach Mars and plunge directly through its atmosphere. If all goes according to plan, the vehicle will shed its outer shell and use rockets to stop its descent at the last moment. Then it will hover above the surface to lower the rhinoceros-sized, nuclear-powered, $2.7 billion Perseverance rover to the dirt via skycrane.
All these robots showing up at almost the exact same time is no coincidence, said Jonathan McDowell, a Harvard University astrophysicist and spaceflight expert.
Mars and Earth are like “runners on a circular racetrack,” he said. “And the really fast runner [Earth] regularly laps the runner just on the outside [Mars]. So sometimes they’re right next to each other, and sometimes they’re on opposite sides of the track.” This Earth-Mars cycle, meaning Earth completely laps Mars, takes about two years to complete.
It would take an enormous rocket, tons of fuel and much more time to reach Mars from Earth while the planets are far away from each other, McDowell told Live Science. But launching while the planets are at their absolute closest — when they are 38.6 million miles (62.1 million kilometers) apart on average — isn’t the most efficient way to get to Mars either.
There’s an earlier point in the planets’ two-year cycle where the journey takes less time and requires less fuel. At that point, which occurs once during the two-year cycle, Earth is a bit behind Mars but continues to move faster than its neighbor. This positioning allows the spacecraft to enter a so-called “Hohmann transfer orbit,” named after German engineer Walter Hohmann, who worked out the underlying mathematics in 1925.
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Here’s how that works:
No rocket carries enough fuel to burn all the way between Earth and Mars, a distance that ranges between tens and hundreds of millions of miles.
That means any interplanetary adventure begins with a brief, intense period of acceleration, followed by a long stretch of coasting. The job of the rocket engines during that initial period of acceleration is to put the spacecraft into an orbit around the sun that will intersect with Mars as soon as possible. The most efficient path between the planets is therefore the solar orbit intersecting with Mars that can be reached with the least expenditure of fuel, and that orbit becomes available once every two years.
But space agencies don’t have to nail that day exactly. As long as they launch during a window of a couple weeks around the date,they can place their spacecraft on Hohmann transfer orbits. Tarry longer than a couple weeks, however, and the trip starts getting much more difficult very quickly.
The Hope orbiter launched July 19, 2020, Tianwen-1 on July 23 and Perseverance on July 30. The gaps between the spacecrafts’ arrivals don’t exactly line up with their launch dates due to minor differences in their rocket technology, trajectories through space and destinations, McDowell said. (It takes a different angle of approach, for example, to plunge directly into the planet’s atmosphere than it does to enter a high orbit as Hope has done.)
It’s not the first time Martian orbital space has been this crowded, McDowell pointed out. The Soviet Union launched four spacecraft to Mars in 1973, though one failed to attain orbit and none of the other three worked as intended upon arrival. Two Soviet spacecraft and one American spacecraft launched to Mars in 1971, and all had at least partially successful missions. (Both nations planned additional probes that year, but the American Mariner 8 probe failed during launch and the Soviet Kosmos 419 never escaped low-Earth orbit.)
What’s different this year, McDowell said, is the sheer diversity of spacecraft reaching Mars, and the fact that several additional probes are already active around the planet. NASA has three orbiters active in Martian orbit, the European Space Agency (ESA) has one of its own and one orbiter that’s a joint project with the Russian Roscosmos, and the Indian Space Research Organization has an active orbiter as well. NASA’s Curiosity rover and InSight lander are also still active on the Martian surface.
Despite that relatively crowded situation, McDowell said he doubts any of the probes will even come within tens of thousands of miles of each other, even if none of the countries had checked their trajectories with each other in advance.
“Space is big,” he said.
Originally published on Live Science.
What we know about the Red Planet from 260 Martian meteorites found on Earth – Firstpost
The ConversationMar 01, 2021 19:23:00 IST
NASA’s Perseverance rover successfully touched down on Mars last month, and has already begun beaming back images. But people might be surprised to learn there have been another 48 missions to the red planet so far. Of these, more than half failed at stages from take-off to deployment — including the 1999 Mars Climate Orbiter, destroyed on Mars entry after someone failed to convert imperial measurements to metric. Successful missions include Mars Insight, which is studying the interior via measurement of “marsquakes”, and the Curiosity rover, which touched down in 2012 and has been examining the geology of Mt Sharp.
Although there have been no return missions, there is a lot we can learn without travelling to Mars — from the more than 260 Martian meteorites that have fallen on Earth.
Images taken by orbiters reveal Mars has more than 40,000 craters, each formed by an asteroid colliding with the surface. You can explore these craters yourself by going to Google Earth, toggling the Google Mars mode and zooming in.
If some of the debris from the large impacts reached escape velocity (about 5 km/s on Mars), it would be able to leave the planet’s gravitational field. Eventually, some of the ejected Martian material has intercepted Earth’s trajectory, flashing through the atmosphere until it either burned up or came to rest on the surface.
Although Martian meteorites have been found across Earth, most have been collected from Antarctica or the deserts of northwest Africa. In both cases, the black crust that forms as the meteorite partially burns up passing through Earth’s atmosphere stands out clearly against ice or sand.
This mode of interplanetary travel is important because it raises the possibility that life could inadvertently travel from one planet to another. Back in 1996, one Martian meteorite, ALH84001, was controversially thought to contain fossilised bacteria.
Some of the older landers have almost certainly taken Earth bacteria to Mars, since they were not purified before launch.
A bubble of Martian atmosphere
Small planets cool quickly and it has long been suspected that Mars’s core has largely but not totally crystallised. This means Mars has mostly lost the protective magnetic field that deflects cosmic radiation.
But we are confident Mars once had an ocean, containing water as we know it. The temperature was above freezing and conditions were suitable for life. The stripping away of the magnetic field early in Mars’s history means this ocean is long gone and the average temperature is now -65℃, but frosts, clouds and ice caps remain.
Not being fortunate enough to roam the deserts of Africa or the icy plateaus of Antarctica, I instead found my first Martian meteorite sitting in a cabinet in a gem store in the small New Zealand town of Akaroa.
Using a scanning electron microscope, my examination revealed it was a shergottite, one of the most common Martian meteorites — equivalent to what we know on Earth as basalt. If it’s basalt, though, how do we know it’s from Mars?
There are several ways of recognising a Martian meteorite. One is from its gas content. When a meteorite strikes the surface of Mars, the “target” rocks are subject to such great pressures they partly melt and trap Martian atmosphere within gas bubbles. Some of these rocks are then ejected from the planet — becoming meteorites themselves.
The thousands of craters scarring Mars’s surface mean it is ancient. This was confirmed when one meteorite was dated to be 4.4 billion years old. Properties of some other Martian meteorites show Mars formed within 13 million years of the formation of the Solar System. This in turn means some of the first planetary crust that formed on Mars likely still exists at the surface.
Old and cold — but not dead
This inference, along with some meteorite mineral and isotopic properties, implies Mars has not been shaped by plate tectonics — the global process that formed the continents, mountain ranges and ocean basins on Earth.
And, as most dated Martian meteorites are less than 1.5 billion years old, volcanism has continued throughout its history. Mars may be cold but it is not dead.
Martian meteorites also hold clues about how people may one day be able to survive on the planet.
While living in hollowed out lava tubes in Martian basalt may appeal to some hopeful interplanetary settlers, we’ll ultimately need to build shelters to protect us from the cosmic radiation and vast dust storms that engulf the planet.
Martian meteorites show olivine, a magnesium-silicate mineral, is common. Experiments are underway to assess the use of a breakdown component, magnesium carbonate, to form a concrete binder from which we could fashion buildings.
Martian meteorites show that big insights can be gleaned from little rocks and reveal what Mars is made of.
Some Of This Year's Official Hurricane Names Are Inspired By Frozen Characters – 915thebeat.com
The official start date of hurricane season is three months away as meteorologists expect a particularly active period this year when three of the anticipated massive storms will be named after Disney characters. The World Meteorological Organization’s list of names for hurricanes in both the Atlantic and Pacific basins includes Olaf, Elsa, and Ana – three characters from Frozen. The film was released in 2013, and the characters’ names were initially placed on the list of hurricane names by the WMO in 2015. This year, the WMO and National Hurricane Center is recycling the list from 2015, as is custom every six years. Names of hurricanes that are unusually destructive are retired and never to be used again.
For Hurricane name information, visit: NOAA (You will be redirected)
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This Tourism Ad for Mars Wraps With a Bleak Jolt of Reality – Muse by Clio
Created by Fred & Farid Los Angeles, the ad begins with an aspirational voiceover: “After more than 5 million years of human existence on Earth, it’s time for a change. Mars: 56 million square miles of untouched land, breathtaking landscapes and incredible views.” You have to look at it from a certain angle—the opposite of Elon’s, really—to feel the irony in its premise.
It ends with a forbidding statement: “And for the 99 percent who will stay on Earth … we’d better fix climate change.”
Ah, the catch: All these promises of adventure, and escape from our existential woes, will likely be reserved for the few who can afford it. (Unless you’re into the whole indentured servitude thing … and hey, if you’ve still got school loans, what’s a couple million more before you die?)
“We wanted to highlight pure nonsense,” said Fridays for Future. “Government-funded space programs and the world’s ultra-wealthy 1 percent are laser focused on Mars … and yet most humans will never get a chance to visit or live on Mars. This is not due to a lack of resources, but the fact that our global systems don’t care about us and refuse to take equitable action.”
To drive that point home, the organization points out that NASA’s Perseverance Rover cost $2.7 billion for development, launch, operations and analysis. While we’re hard-pressed to begrudge NASA a budget at the worst of times, it’s hard to look at that figure and think about the fact that we still haven’t figured out recycling.
The ad went live on Feb. 18, the day Perseverance landed on Mars. Contrast this date with another one, just a smidge down the road: Elon Musk is “highly confident” that SpaceX will get people there by 2026. (Though if that projection is anything like his Tesla ones, feel free to add 5-10 years to that with confidence.)
This marks Fred & Farid LA’s third collaboration with Fridays For Future. It follows “House on Fire” and “If You Don’t Believe in Global Warming, How About Local Warming?” The hope, in this case, is that some bleak sci-fi will finally be what motivates people to action.
Tell that to Greta Thunberg.
On the other hand, if you’d like some actual sci-fi with a spin on what happens to everybody on Earth when all the Well-Heeled People leave, we recommend N.K. Jemisin’s Emergency Skin. (Bonus points: Buy it at a Black-owned bookstore. Thanks to Oprah, you can find one by state.) It’s short and surprisingly optimistic—so optimistic that we actually worry the most exploitative wealthyfolk will instead choose to stay, which in our minds seems increasingly likely.
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