Every New Year begins with the best intentions. Vaccine-makers promise vast deliveries. Governments plan rapid roll-outs of same. Citizens vow to drink less and exercise more. Hedge-fund managers pledge to make millions by shorting under-performing stocks. Many of those expectations get downgraded.
But if the prospect of a less-than-stellar start to the New Year has you down, take heart. There’s another one coming on Feb. 7 — on Mars.
Martian New Year shouldn’t be confused with the lunar New Year (a.k.a. Chinese New Year), which doesn’t take place on the moon. Calculated through a combination of solar and lunar cycles, Chinese New Year falls this year on Feb. 12. Happy 4718!
Martian New Year is a much more recent creation. Feb. 7 marks the beginning of the year 36. Back at the turn of the (Earth) century, with the first rover already on the red planet and more on the way, scientists decided they needed a way to count Martian years. Earth years wouldn’t do, since Mars takes 687 days to circle the sun.
They picked the Martian spring equinox of 1955 as the start of year one. This handily predated any space missions — the first successful flyby was in 1964 — and coincided with a dust storm on the planet widely observed from Earth. Later, astronomers backdated this to include a year zero. With no prophets or deities to draw on, years before that just take a minus sign.
To talk Martian time, I reach out to Emily Lakdawalla, a planetary geologist, educator and author — her next book, Curiosity and Its Science Mission, is about the rover that landed on Mars in August of 2012 (Martian summer of 31) and is still roving.
It’s just close enough to lull you into thinking they’re the same length. And just far enough apart to mess you up
“Although I wasn’t aware it was coming, I was actually chagrined that I was not aware it was coming,” she says of the upcoming Martian holiday from her home in California. “Certainly anybody who cares about surface operations on Mars cares about the Martian New Year. It signals a change of the seasons, just as it does on Earth. And that’s actually really important for landed Mars missions.”
Mars, like Earth, has an elliptical orbit that brings it closer to the sun at certain points of the year. It also has an axial tilt of 25 degrees. (Earth’s is just over 23.) Together this creates seasons, with variations in temperature, sunlight and even air pressure, since some of the thin carbon dioxide atmosphere freezes at the poles in the winter. Lakdawalla says the overlap of tilt and orbit means northern Martian winters are significantly milder than in the south, with repercussions on any rovers operating in that hemisphere.
In addition to its own years and seasons, Mars has its own days, commonly called sols. Pronunciation is up for grabs – you’ll hear both “sole” and “soll” in the movie The Martian , for instance – but the word was coined by John Newcomb, a NASA engineer who worked on the first robotic lunar orbiters, and later on the Viking Mars landers in the 1970s. Back then, scientists were referring to the “Mars mean solar day,” and Newcomb suggested a shorter version that stuck.
Nick Peper, a systems engineer on the team that operates the Curiosity rover, notes that a sol is almost the same length as a day, but that slight difference can cause problems. Earth’s day is 23 hours and 56 minutes long, the rounding of which gives us a leap day every four years. But a sol is 24 hours 39 minutes, or about 3% longer than a day. About once a month, the two line up briefly.
“It’s not something we can keep up as an operations team for years and years,” says Peper. “Spending half of your time awake at night probably wouldn’t work.” Instead, science teams push their working days a little earlier or later to approximate Martian time, or they’ll figure out an extra sol or two of work for the rover, “so we don’t have to plan at night.”
The exception is when a mission first lands, as is expected this month when the Perseverance rover makes Mars-fall after almost seven months in interplanetary space. Landing is expected on Feb. 18.
“Most Mars missions, when they land, will operate on Mars time for a [couple of months],” he says. This is “to maximize the amount of stuff they can get done, so they can use every day to its fullest.” Or every sol.
NASA once went so far as to order Mars wristwatches, which kept time by the red planet’s reckoning. Peper has a readout of Martian time in the corner of his computer screen. As we chat, he informs me that the same sun that is shining brightly on Pasadena at 10 a.m. Pacific Time, and struggling to break through the cloud cover over Toronto at 1 p.m. Eastern, is just now rising over Gale Crater and Curiosity, at 6:51 a.m. local Mars time.
To keep Martian morning from drifting away from the actual sunrise, scientists merely lengthen each second, minute and hour on Mars by a factor of 1.02749. So a sol on Mars is 24 hours long, but every hour is a little long than its equivalent on Earth.
It’s a good fix, though perhaps not as poetic as the one imagined by science-fiction author Kim Stanley Robinson, who in his Mars trilogy writes of “the timeslip,” when clocks stop every sol at midnight for 39 minutes. Confusingly, rovers’ internal clocks measure time in Earth seconds, which is then converted as needed.
I ask Lakdawalla if she thinks human explorers to the red planet will keep time the Martian way. “I don’t see any reason why you would change that,” she says, “because it’s a clock time that simply divides the day into reasonable intervals. Now, at some point in the future, maybe when we’re spacefaring, it seems to me like it wouldn’t be a bad idea to adopt some kind of metric time system.” But for now, Martian time “works very well.”
Peper agrees. “That extra increase in day length is probably small enough that the human diurnal cycle could adapt to it,” he says. Even so, future missions might favour night-people over morning-people, since astronauts on the surface would be going to bed almost 40 minutes later every single sol.
“It’s just close enough to lull you into thinking they’re the same length,” Peper says of Martian time units. “And just far enough apart to mess you up.”
And while he says he has never celebrated the Martian New Year, he notes that Curiosity recently passed its 3,000th sol on Mars. He and his team marked the occasion, despite the fact that in Earth time — 3,082 and a half days — it was not a round number. Due to the pandemic, he says, “this year was a little bit subdued, but the team usually gets together for either the earth-year celebration of when we landed, or sol milestones.”
There is one final oddity of Mars time, but it pulls us into the realm of relativity. What time is it on Mars right now?
It seems like an easy question to answer — you can picture a rover sitting on the planet right now — but it turns out that there is no “universal now” that unites Earth and Mars. Asking when now is on Mars makes as much sense as asking where “here” is in Beijing. It isn’t. Beijing has its own “here.”
“You always have to ask that question when you’re talking about events in Mars time,” says Lakdawalla. “And at landing times is when it gets especially confusing. Because the now for us is when the radio signals reach us. And so by the time the signal of Curiosity hitting the top of Mars’ atmosphere has reached Earth, everything will be over on Mars.” She waves her hands vaguely. “According to some mythical simultaneity thing.”
She adds: “That sort of works if you don’t think about it too hard. That’s not the kind of stuff I like to do. I’m a geologist; I like physical objects.”
Regardless, on the day we on Earth call Feb. 7, Mars will cross a point in its orbit known as solar longitude zero degrees, or Ls0, pronounced “ell sub ess zero.” If you want to make some noise or raise a glass of Champagne to that pale red dot in the sky, go for it. You won’t get the chance again for another 668 sols. That’ll be Boxing Day, 2022 here on Earth, and New Year’s Day, 37 on Mars.
Copyright Postmedia Network Inc., 2021
