התחנה תאפשר לאסטרונאוטים לאסוף סלעים מהירח, כמו הדוגמיות שהובאו בתכנית “אפולו”, ולמיין ולנתח אותן בתחנה, לפני החזרתן לכדור הארץ – נאס”א
תחנת החלל הבינלאומית המקיפה את כדור הארץ מאז 1998 ומאוישת דרך קבע מאז שנת 2000, מתקרבת לימי קיצה. שתי השותפות העיקריות בתחנה, סוכנות החלל האמריקנית נאס”א וסוכנות החלל הרוסית רוסקוסמוס, מתכננות להפסיק לתקצב את המבנה היקר ביותר בהיסטוריה – שבנייתו נמשכת כל הזמן עד ל-2024.
מה תוכנן להמשך הדרך בחלל? נאס”א מעוניינת לבנות את תחנת החלל הבינלאומית הבאה סמוך ירח. התחנה תשמש את המדינות החברות בה כפלטפורמה למשימות מאוישות לירח, וכן גם עבור המשימה המאוישת הראשונה המתוכננת למאדים. לאחרונה החליטה ממשלת קנדה להצטרף רשמית למאמצים, עם התחייבות של ראש הממשלה, ג’סטין טרודו, להשקיע מיליארד וחצי דולר בבניית זרוע רובוטית חכמה, שתשמש לתיקונים ולתחזוקת התחנה, בדומה לזרוע שיוצרה על ידי קנדה וממשמשת כיום את תחנת החלל הבינלאומית.
קנדה מבטיחה עוד לבנות זרוע רובוטית קטנה ורגישה יותר, בדומה לרובוט הפועל בתחנת החלל הבינלאומית הנוכחית. הזרוע הרובוטית החכמה המיועדת לתחנת החלל החדשה, שלא כמו זו של התחנה הקיימת, תהיה אוטונומית לחלוטין. למה כוונה בעצם? לפי התכניות תחנת החלל שתמוקם לייד הירח, תהיה מבצעית בכל מצב וגם כשלא יהיו אסטרונאוטים על סיפונה.
כחלק מההתחייבות בת העשרים וארבע השנים, קנדה מתכוונת להקצות משאבים גם לעידוד עסקים קנדיים קטנים ובינוניים לפיתוח טכנולוגיות למשימות מאוישות לירח. זאת בדומה למכרזים שפרסמה לאחרונה נאס”א לפיתוח מערכת נחיתה מאוישת לירח.
בשנת 2017 חתם נשיא ארה”ב, דונלד טראמפ, על צו נשיאותי המורה לנאס”א לחזור ולנחות על הירח. לכן ייתכן שכבר בשנים הקרובות נראה אסטרונאוטים אמריקניים על הירח, עוד לפני השלמת התחנה הסמוכה לו. קנדה היא המדינה הראשונה שמצטרפת לארה”ב בהתחייבות כספית לבניית תחנת החלל החדשה.
לפי התכנית החלק הראשון של התחנה שיכלול את מערכות ההנעה והחשמל, ישוגר בשנת 2022. מעבורת החלל המאוישת הראשונה שתהיה אמריקנית, תצטרף אליו כבר בשנת 2024. התחנה תקיף את הירח במסלול אליפטי מאוד סביב נקודת לגראנז’ 2, נקודה יציבה יחסית בין מסות הארץ והירח (כשהוא נע במשך שישה ימים במרחק של בין 70,000 ק”מ ל-1,500 ק”מ מפני השטח של הירח). משימות מאוישות ובלתי-מאוישות יעגנו בדרכן לירח, למאדים וליעדים רחוקים יותר, כאשר בשנות ה-30 של המאה ה-21 צפויה המשימה המאוישת הראשונה למאדים להשתגר מהתחנה. לתחנת החלל סמוך לירח יכולים להיות יתרונות גדולים ומשמעותיים על פני שיגורים ישירים מהארץ לירח או מהארץ למאדים. כך למשל התחנה תאפשר לאסטרונאוטים לאסוף סלעים מהירח, כמו הדוגמיות שהובאו בתכנית “אפולו”, ולמיין ולנתח אותן בתחנה, לפני החזרתן לכדור הארץ. בנוסף כפי שיודע כל מי שצפה בסרט האימה המדע הבדיוני “לייף”, את הדוגמיות הראשונות ממאדים רצוי לנתח בתחנת חלל לפני שמנחיתים אותן על כדור הארץ. זאת בשל החשש לזיהום ביולוגי כאן.
אבל אולי היתרון הגדול ביותר של התכנית, לדעת התומכים הרבים שלה, נעוץ באפשרות לבנות מחדש ובביטחה יחסית את יכולות האסטרונאוטים וסוכנויות החלל בחלל העמוק. יש לזכור שמאז סיום תוכנית מעבורת החלל בשנת 2011, הנוכחות האנושית בחלל הוגבלה לשיגורים של חלליות רוסיות מסוג “סויוז” לתחנת החלל הבינלאומית, שמקיפה את כדור הארץ במסלול לווייני נמוך מאוד של כ-400 ק”מ מפני הים. התחנה תאפשר לבדוק את הכלים החדשים, כמו מעבורת החלל “אוריו” בחלל העמוק, ומבלי לסכן את אנשי הצוות במשימה ישירה לירח. בוודאי גם לא לסכנם במשימה בת שנה ויותר למאדים.
Saturn’s main rings, along with its
moons, are much brighter than most stars. As a result, much shorter exposure
times (10 milliseconds, in this case) are required to produce an image and not
saturate the detectors of the imaging cameras on Cassini. A longer exposure
would be required to capture the stars as well. (photo from NASA/JPL-Caltech/Space
Science Institute)
Grand Finale was the official name of Cassini’s
last act: a risky orbit between Saturn’s rings and atmosphere in an attempt to
explore the planet up close, right before the craft went up in flames.
Prof. Yohai Kaspi and Dr. Eli Galanti of the Weizmann
Institute’s earth and planetary sciences department led one of the studies on
Cassini’s final mission, revealing the depth of Saturn’s jet streams – the
strongest measured in the solar system, with winds of up to 1,500 kilometres
per hour – and found them to reach a depth of around 9,000 kilometres. Teaming
up with research partners in Italy and the United States, their study also
helped reveal the age of the planet’s rings. The findings of these studies were
published this month in Science.
Cassini was one of the more successful
planetary missions, orbiting and returning information on Saturn and its moons
for the last 20 years. As the mission was approaching its end, it was decided
to end its life with a non-circular orbit swinging in very close to the planet,
followed by a final plunge into the gaseous mass. Kaspi and Galanti joined the
Cassini team following their work as part of NASA’s Juno science team, which
had employed a similar orbit to produce the most reliable measurements yet of
Jupiter’s atmospheric depth. The Cassini scientists thought it would be
possible to do the same for Saturn, and the Weizmann scientists were called in
to apply their methodology to the Saturn measurements.
Kaspi described the challenge: “We detect small
variations in the gravity field as the craft orbits Saturn, and translate these
into the atmospheric wind that produces them. There was no guarantee it would
work for Saturn, as the gravity signal on Saturn is more difficult to interpret
than what we had on Jupiter. We discovered that not only did it work for both
planets, but that same physical processes control the depth of the flows on
these two planets.”
To calculate the depth of the winds, the
gravity measurements undertaken by Cassini were analyzed with the theoretical
model developed by the Weizmann researchers. “We also teamed up with a second
group investigating the internal structure of the planet,” said Galanti.
“Together, we calculated that the depth of the atmosphere is up to around 9,000
kilometres. That is three times deeper than that of Jupiter. We also found
that, just as on Jupiter, a strong internal magnetic field is what limits the
depth of this layer of the atmosphere. Our theory worked twice, which provides
strong support for its validity.”
In the same study, the researchers analyzed the
Grand Finale data from Saturn’s rings, finding they are at most 100 million
years old. That is quite recent in the 4.5-billion-year history of the solar
system. The planet in the night sky at the time of the first dinosaurs was,
apparently, without the rings we know today.
For more on the research being conducted at the Weizmann Institute, visit wis-wander.weizmann.ac.il.
– Weizmann Institute
Saturn losing its rings
New NASA research confirms that Saturn is
losing its iconic rings at the maximum rate estimated from Voyager 1 and 2
observations made decades ago. The rings are being pulled into Saturn by
gravity as a dusty rain of ice particles under the influence of Saturn’s
magnetic field.
Saturn’s northern hemisphere in 2016, as that part of the planet nears its northern hemisphere summer solstice in May 2017. Since NASA’s Cassini spacecraft arrived at Saturn in mid-2004, the shifting angle of sunlight as the seasons march forward has illuminated the giant hexagon-shaped jet stream around the north polar region, and the subtle bluish hues seen earlier in the mission have continued to fade. (photo from NASA/JPL-Caltech/Space Science Institute)
“We estimate that this ‘ring rain’ drains an
amount of water products that could fill an Olympic-sized swimming pool from
Saturn’s rings in half an hour,” said James O’Donoghue of NASA’s Goddard Space
Flight Centre in Greenbelt, Md. “From this alone, the entire ring system will be
gone in 300 million years, but add to this the Cassini-spacecraft measured
ring-material detected falling into Saturn’s equator, and the rings have less
than 100 million years to live. This is relatively short, compared to Saturn’s
age of over four billion years.” O’Donoghue is lead author of a study on
Saturn’s ring rain appearing in Icarus Dec. 17.
Scientists have long wondered if Saturn was
formed with the rings or if the planet acquired them later in life. The new
research favours the latter scenario, indicating that they are unlikely to be
older than 100 million years, as it would take that long for the C-ring to
become what it is today assuming it was once as dense as the B-ring. “We are
lucky to be around to see Saturn’s ring system, which appears to be in the
middle of its lifetime. However, if rings are temporary, perhaps we just missed
out on seeing giant ring systems of Jupiter, Uranus and Neptune, which have
only thin ringlets today,” O’Donoghue added.
Various theories have been proposed for the ring’s
origin. If the planet got them later in life, the rings could have formed when
small, icy moons in orbit around Saturn collided, perhaps because their orbits
were perturbed by a gravitational tug from a passing asteroid or comet.
This JunoCam image highlights Oval BA. (photo from nasa.gov)
The U.S. National Aeronautics and Space Administration (NASA) recently released the first findings of the Juno research spacecraft, which entered Jupiter’s atmosphere last year.
The Weizmann Institute of Science’s Dr. Yohai Kaspi is a senior member of the Juno mission team. The reason why this research is so important, he said, is because it will allow us to better understand how the solar system was formed.
“To do that, we really need to understand Jupiter and how it was formed because, then, we can understand earth, in sequence,” said Kaspi.
Dr. Yohai Kaspi of the Weizmann Institute of Science. (photo from WIS)
For Kaspi, the fascination with space came at the early age of 7, when his dad shared some pictures of the Voyager I and II and took him stargazing. His interest grew from there, including when he was navigating in the Negev while in the Israel Defence Forces.
“My hobby growing up was competitive sailing,” said Kaspi. “That drew my interest into meteorology and understanding why the wind blows the way it does. Growing up in Nahariya, which borders Lebanon … all kinds of stuff [are] coming from Lebanon – currents, trash. It was very obvious where the wind or current was coming from and that connected to sailing.”
Kaspi studied math and physics at Hebrew University before heading to the United States, seeking adventure and a doctorate at Massachusetts Institute of Technology. Soon after, he was recruited to be a professor at the Weizmann Institute of Science.
While at MIT, Kaspi became connected to the Juno mission, developing instruments to help measure atmospheric conditions on Jupiter.
“I was interested in space and the weather,” said Kaspi. “I studied meteorology, as it kind of brings them together … [with] planetary science. We have planets, which resemble earth in some aspects, but we don’t understand their features and circulation.”
While Jupiter is by far the biggest planet in the solar system (11 times the diameter of earth) and has the greatest mass (300 times that of earth), it is a gas planet (i.e. it has no liquid or solid parts). Kaspi has studied Jupiter’s different weather zones and deltas.
“I developed a theory for understanding how deeply they extend,” said Kaspi. “When you look at Jupiter, you have this red and white belt, or zone. That’s all at the cloud level, so it condensates at the same temperature. But, we have no information what’s happening underneath them. What we needed was a global way to survey what was happening underneath the cloud layer. And that’s exactly what Juno is.
“During my PhD, I developed a new method to relate between the gravity field of the planet and the flows underneath this cloud layer. To understand Jupiter, we need to understand what’s happening in its interior.”
Kaspi has been involved with Juno since 2008, along with 30 to 40 other scientists who form the core of the mission, developing and designing the experiments, and interpreting the data.
This enhanced colour view of Jupiter’s south pole was created by citizen scientist Gabriel Fiset using data from the JunoCam on NASA’s Juno spacecraft. (photo from nasa.gov)
“We’re trying to deduce the depths of the flows from the gravity measurements of the planet,” explained Kaspi. “The purpose is to see what’s happening inside the planet. It has nine instruments and each one probes in different ways what is happening in the planet’s interior.
“One is a gravity instrument…. We send a beam from the spacecraft to earth. The beam travels 800 million kilometres and reaches earth. A desert in California captures that beam.
“We try to see the accelerations and decelerations of the spacecraft around the planet … trying to understand … the flow field and the gravity field of Jupiter.”
It was only when we first saw earth from space that we were able to understand the changing atmospheric conditions that are part of what is largely considered part of climate change, said Kaspi.
“We’d be able to understand how the solar system was formed, including earth,” he said of one of the project’s possible results. “For example, it’s really important for us to know if there’s a core inside Jupiter. A planet with a big or small core would have a different effect on the gravity field. When we measure the gravity field, we can deduce what’s happening deep inside the planet, which would lead us to different theories of how the solar system was formed.
“The connection to earth is we see the objects of Jupiter’s atmospheres … we don’t understand their strengths, how wide they are and how deep they are. We don’t have theories for that. If you want to have a good understanding of objects on earth, you have to look at the sister planet.”
The data-collecting portion of the Juno mission will come to a close at the end of this year. After 10 years of research and six orbits, the data will be analyzed to determine the direction of the mission going forward.
“We have already a lot of good data and we’re reaching a point where we can have significant results for understanding the structure, depths and composition of the atmosphere, but it’s a process,” said Kaspi. “Basically, we have one measurement every 53 days. So, every 53 days, I get my stuff and go to the U.S. and stay there for a week, analyzing the data and analyzing it for the rest of the 45 days, and then go back.”
Regardless of the results, Kaspi will continue the work he is doing at the Weizmann Institute on climate change and working on an instrument that will be sent to Jupiter on board the 2022 spacecraft being built by the European Space Agency.
“It will be the first Israeli instrument that will go beyond earth’s orbit,” said Kaspi. “That’s exciting. So, we’re involved in that and a variety of projects, trying to achieve fundamental understanding.”
As far as space exploration for the purpose of finding another planet fit for human dwelling, Kaspi said, “I’m just going to say that, if there is life in the solar system, it might be in the moons of Jupiter … because they have liquid water, a deep ocean, tens to hundreds of kilometres deep. Maybe there is life there.”
