The night sky. Nightly news begins right now. Good evening, it may have been a warm day in new york city, but there was a winterlike chill in the room at the United Nations when president obama and Russias Vladimir Putin came face to face. With relations between the two governments at a low point, the two leaders sat down late today for their first formal meeting in a very long time, but not before airing their differences in speeches before the u. N. General assembly where putin managed to seize the agenda and the headlines. Heres nbc news chief Foreign Affairs correspondent, andrea mitchell. Reporter Vladimir Putin and barack obama in their first formal oneonone meeting in two years. Only after trading insults today over syria. Did you Work Together . Reporter putin swaggered into the u. N. After a diplomatic military and p. R. Blitz to seize the initiative from the u. S. That left the white house scrambling. Obama wants syrian president assad out. But putin said without assad, isis would take over, insisting its an enormous mistake to refuse to cooperate with the Syrian Government and its armed forces who are valiantly fighting terrorism face to face. Obama scornfully rejects that argument. In accordance with this logic, we should support tyrants like Bashar Al Assad who drops barrel bombs to massacre innocent children. Reporter obama and putins icy relationship is being called a new cold war. Not just over syria but ukraine. Obama slapped sanctions on putins cronies for supporting separatists there. Today putin arrived 20 minutes late for the u. N. Lunch, sitting so close to obama they had to shake hands and couldnt avoid the toast. This is not reagan and gorbachev or clinton and yeltsin. This is not the vlad and barack show. No, its a business relationship. Theyve spoken on the phone and are blunt and direct with one another. Reporter putin watchers say he sees every rivalry as a sports match, a contest he must win. Putin shows himself as a macho man. Hes a strong man. He sees weakness and seizes on it. Reporter on the u. S. Policy in syria, he sees weakness. Just a handful of rebels trained at huge cost and isis ranks growing. When asked on 60 minutes whether he thinks obama considers him an equal translator well, you ask him. Hes your president. How could i know what he thinks . Reporter there are consequences to their bad relationship. The syrian war and the refugees fleeing from it is the biggest humanitarian disaster since world war ii, and its dragged on this long because russia and the United States cannot agree on how to end it. Lester . Andrea mitchell, thank you. Hes been accused of being heavy on bluster and light on policy, but feeling the heat from opponents gaining in the polls, donald trump is getting specific, rolling out a tax plan today that he says is simply common sense. Some of those who have punched the numbers suggest its a gift for the wealthy. All of it happening as Hillary Clinton rolls out what could be a new but familiar strategy to combat her email troubles. In an interview with nbc news, we have two reports. We begin on the trump plan. Break it down for us. Reporter lester, gone are the days of a flat tax. This is a graduated tax. Despite what hes been saying on the campaign trail, economists across the political spectrum say the plan could benefit the wealthy even more than the middle class. [ applause ] in the lobby of his manhattan skyscraper, donald trump got down to details today. Its going to cost me a fortune. Reporter releasing an ambitious tax plan that his Campaign Says would get rid of income tax for millions of americans while lowering rates for the rich. Under the plan, individuals making less than 25,000 and married couples making less than 50,000 would pay no income tax. The highest tax rate would drop from 39. 6 to 25 . Estate taxes would be eliminated. Businesses would pay 15 . And overseas profits would be taxed one time at a rate of 10 , which trump claims would bring more than 2 trillion back to the u. S. The cuts combined with unspecified loopholes and deductions would all lead to a flourishing economy. Were looking at a 3 but think it can be 5, it could even be 6. Well have growth that will be tremendous. Reporter from the details it appears this is a significant tax cut for the richest taxpayers. Reporter trumps tax plan, another big promise for a big fix from the frontrunner. On infrastructure our bridges are falling apart. Our roads are a mess. Everything, its a mess. Reporter estimates put rebuilding at 3. 6 trillion by 2020. On health care, specifically repealing and replacing obamacare we will have a plan that will be so good reporter repealing alone 137 billion over a decade. Trump getting specific. But as the experts weigh in, the candidate may soon find out the devil really is in the details. Qa katy tur, nbc news, new york. Im Kristen Welker in washington where secretary clinton is trying to dig herself out of the email controversy. Im not by any means a technical expert. Well, it is like a drip, drip, drip. Reporter now explaining again why emails surfaced dated two months earlier than clinton initially said she set up the personal account. Explain that. There was a transition period. You know, i wasnt that focused on my email account. Reporter clinton has turned over 55,000 pages of emails from her personal account dating back to march, 2009. Today her campaign acknowledged she sent emails as early as january of that year. The explanation she started using the account before the server was officially set up at her home. Every phrase and every sentence that she utters is examined minutely by the press, by her critics, by everyone, and that makes it hard for her to kind of tamp down on the controversy. Reporter her new weapon her husband, whos set to play a bigger role in the campaign. It really is similar to the strategy that the republicans employed against me with whitewater. Its they look at the field and say who do we not want to run against. Reporter for her part, clinton is also focusing on policy and points out as secretary of state she advocated arming rebels in syria before the president came around to her view. This is a failure in policy, isnt it . It is. And when i recommended it, it was several years ago. I cant sit here and tell you that if we had done what i and others had recommended we would have made more progress on the ground. Reporter and whether asked if she would have a place for her husband in the west wing hes a pretty busy guy. I dont know anything like that. But im not looking im not counting my chickens before they hatch. Reporter the drip of Clinton Emails continues this week with the state department set to release more on wednesday. As for bill clinton, he plans to attend several fundraisers for his wife this fall, beginning thursday in atlanta. Later he goes to missouri and michigan. Lester . All right, thank you. Lets bring in our political director, moderator of meet the press, chuck todd. Lets start with new poll numbers youre releasing tonight about the state of the race and potential candidacy of joe biden. It highlights the weakness now of Hillary Clinton. Our poll shows that joe biden and Bernie Sanders both polled better against donald trump, the current republican frontrunner, in a general election than Hillary Clinton. Look, biden up by 21 points. Sanders by 16 points. Clinton, only up by 10. A sign of how much trouble shes having with swing voters. By the way, the most popular candidate running now is not running joe biden. Lets talk about the republican side. What do you see there . Its trump, carson, fiorina. When you add up the vote, the outsiders unelected, their vote adds up to 52 . The majority of the republican primary elective. Look at the candidate in double digits, marco rubio. The only other candidate in double digits. He has an interesting strength, hes an insider and sitting senator. Some view him as a potential outsider because hes a new face. As this thing shuffles out, he could be the sort of establishment guy standing against the alternate to trump. Weve got a way to go, but the rubio numbers are a big deal. Speaking of whats going on the hill, we have a candidate for speaker of the house, kevin mccarthy. Well see if hes able to do what Speaker Boehner wasnt able to do keep those House Republicans together. All right, chuck todd, good to have you here. Thank you. Now to the amazing discovery in the search to answers to one of lifes biggest questions are we alone in the universe . Nasa scientists revealed breakthrough evidence of flowing water on mars. Now that is fueling speculation there may be life out there, too. Nbcs Gabe Gutierrez reports. Reporter its long been seen as the mysterious red planet. Dark, dangerous, and dry. Today, nasa announced a discovery that is out of this world. Liquid water has been found on mars. Reporter a new study provides the strongest evidence yet that theres flowing water on modern mars. Using instruments on an orbiter circling since 2006, researchers detected hydrated salts in these streaks. They show up when the temperature rises and disappear when its colder. Could this mean that theres life on mars . It means that theres the potential for life on mars. Reporter georgia tech assistant Professor James ray is one of the studys coauthors. What we see for the first time is an actual detection of the water molecule. Basically the smoking gun. Reporter for years, scientists had known that there was some water on mars, but it was frozen solid in polar icecaps. These streaks snaking down mountains now suggest liquid water. I think within the next 20 years, well have astronauts at least around mars and hopefully on the surface very soon after. In space reporter in a cosmic coincidence, the martian debuts in theaters this week, starring matt damon playing an astronaut stranded on mars. A planet where nothing grows. Reporter todays discovery got the families dreaming at the fern bank museum of Natural History in atlanta. Would you like to visit mars . Why would you want to visit mars . Because its cool, and there are aliens there, too. Theres so much we dont know yet. Pretty cool. Reporter still a mystery, the waters source. Is it from underground or the atmosphere . Either way, life beyond earth, once thought Science Fiction now within sight. Gabe gutierrez, nbc news, atlanta. Pope francis is back at the vatican this evening after his historic visit to america and also to cuba. A trip that included nearly 12,000 miles of travel, 26 speeches, and 14 rides in the popemobile. And everywhere he went, he got the kind of welcome not soon forgotten. Nbcs Anne Thompson covered the popes trip and reports from rome. [ cheers ] reporter from the sustained standing ovation at Madison Square garden [ cheers ] reporter to a tender moment with 10yearold Michael Keating and his mom and the nine babies kissed on his final popemobile ride alone, pope francis says he was surprised how warm and lovable the American People were. On flight back to rome, the pope shared his impressions of each city with reporters. Washington reporter he said washington was warm but more formal. New york, a bit exuberant. And philadelphia, very demonstrative. People who had felt a distance from the Catholic Church for a variety of reasons, many are talking about how they feel drawn to him and even more drawn to him after this. Reporter francis insisted he was not downplaying the sex abuse scandal when he praised bishops for facing it with courage. On the plane, he called child abuse by a priest a near sacrilege and anyone who covered it up, even bishops, guilty. [ speaking native language ] reporter he said Conscientious Objection is a human right even for officials. But the pontiff who spoke about religious liberties did not specifically refer to the kentucky clerk who refused to issue marriage licenses to gay couples for religious reasons. Reporter as for pope francis superstar, the famously humble man told reporters such things as fame are temporary, what lasts is being a servant to god. For the american church, now the question is will there be a lasting francis effect . Will disaffected catholics come home to stay, or will this trip just be a pleasant memory . Lester . Anne thompson outside the vatican. Thank you. Sobbing before a judge, saying she regretted making a horrible mistake, today joyce mitchell, the woman who helped two convicted murderers break out of a maximum security prison in upstate new york, was sentenced to up to seven years behind bars for her role in the escape. The sentence was part of a plea deal. Mitchell apologized for the fear and disruption caused by the escape and manhunt which went on for three harrowing weeks. Still ahead tonight, the rising cost of your breakfast. Whats behind the sudden spike in prices for something thats been part of the morning routine for decades in so Many American kitchens. Also, tensions exploding between teammates. Fallout and the fight in the dugout. The season over for one of these players. Were back now with the price you pay and something youve probably noticed at the supermarket. The price of cereal is on the rise. One of many things in the grocery aisle getting more and more expensive. Cereal is rising faster than a lot of other products, amid changing tastes in the american breakfast. As nbcs rehema ellis reports. Reporter sticker shock in the cereal aisle. The morning staple is getting more expensive. Do you worry about the price of cereal . Yes, i do. I have three children, and they love cereal. So i only buy it if its on sale. Reporter from flakes to loops and puffs, the cost of cereal has steadily risen. Escalating faster than other groceries. Over the last five years, the price of a pound of cereal climbed 20 cents to 3. 09. At the same time, people are eating less of it. Shoppers will spend 9. 5 billion on cold cereal this year. Thats down 7 since 2012. Analysts say shoppers are looking for healthier and faster foods. Theyve gone to greek yogurt. Theyve gone to power bars. Anywhere that they can get that protein thats going to give them the right energy and the right nutrition for the day is what theyre seeking out. Reporter while some brands have made efforts to make their cereals healthier by cutting sugar and boosting fiber, experts say many havent done enough to innovate. Cereal is going through the same thing that soda is going through. Theyve got to get better quality ingredients. They have to be more nutritious. Reporter as demand for cereal falls, companies have been shrinking packaging and cutting back on coupons to raise profits. Still, cereal remains a morning mainstay, as 90 of american households say they buy it. I like cereal. Its easier, quicker. And it tastes better. Reporter even though the rising cost is making cereal harder to swallow. Rehema ellis, nbc news, wayne, new jersey. Were back in a moment with the multibillion dollar gamble that just went bust at the top of the world. How much money do you have in your pocket right now . I have 40, 21 could something that small make an impact on something as big as your retirement . I dont think so. Well if you start putting that money towards your retirement every week and let it grow over time, for twenty to thirty years, that retirement challenge. crowd cheering . Might not seem so big after all. Prudential, bring your challenges. After pouring 7 billion into its search for oil in the arctic, Royal Dutch Shell announced today it was calling it quits. Shell says it did find oil and gas in an exploratory well, but it wasnt enough to continue drilling. Our Cynthia Mcfadden toured alaska with shells north America President four weeks ago. At the time, he was cautiously optimistic about the operation. Today he said the news was disappointing. Shell won approval to drill from the Obama Administration in midaugust for the first time in 24 years. It was a move fiercely fought by environmentalists and some of the locals. A fascinating snapshot showing how immigration is reshaping our country. A new pew study finds that 13. 7 of the Current Population was born outside the u. S. The number is expected to hit a record 14. 9 by 2025. Also notable, 47 of immigrants in the u. S. Are hispanic. 26 are asian. After the middle of the century, asians are expected to pass latinos as the largest immigrant group. After a nasty dugout scuffle in which nationals reliever Jonathan Papelbon grabbed bryce harper by the throat yesterday, the team has suspended papelbon for four games, combined with a League Suspension for a separate incident last week. Hes done for the season. Appears he was angry at harper for not running out a flyball. Harper was also out of the lineup for todays game. Some old american favorites are vying for a place in the National Toy Hall of fame which has announced a dozen finalists for this years induction. Among them are the spinning top, the scooter, coloring books, playmobile and puppets, also teenage mutant ninja turtles, super soakers, the wiffle ball, American Girl dolls and games including battle shiship, jenga, and twister. Only two will make the cut. When we come back, the spectacular show in the sky that wont be seen again for 18 years. Developing news. A husband and wife killed in their own home. Take vo who deputies say may be to blame for the double homicide. Janelle take vo plus, an accident, or a dangerous trap for cyclists . The troubling discovery on a popular bay area bike route. Next close the news is next. Finally tonight, mars may be getting all the headlines today, but thats not what had so Many Americans gathering late last night to look up at the sky. The greatest show on earth was the moon, and a rare celestial event that wont happen again for a long time to come, resulting in spectacular views. Heres nbcs joe fryar. Its beautiful. Reporter you didnt need cable or an Internet Connection to see it. Yet the ratings for this show were huge. Its coming out behind the clouds. Its amazing. Reporter millions around the globe peering skyward to catch a glimpse of the super blood moon. Probably the best moon we have. Reporter across the globe, a similar sight, just different foregrounds. From an english countryside to the eiffel tower, from the Washington Monument to a kansas farm field. Stunning images filled social media, along with plenty of lowgrade cell phone shots where the moon looked more like a street light far off in the distance. Still for many, this was something to celebrate. Big things are going to happen. Youve got to be ready. Reporter so how does a blood moon even happen . Start with a full moon on its closest approach to earth so it looks up to 14 larger. Thats called a supermoon. Now add a Lunar Eclipse where the moon passes directly behind the earth into our planets shadow. Sunlight is filtered through the earths atmosphere creating a red tint. Ive seen pictures of it, but ive never like really imagined it would be like this cool. Reporter this was the First Time Since 1982 that a supermoon coincided with a total Lunar Eclipse. If you missed it, you wont see another one until 2033. Some feared it was a sign of the worlds end. Maybe it just brought the world a little closer. All of us united beneath one supermoon. Joe fryer, nbc news, new york. That will do it for us on this monday night. Im lester holt. For all of us at nbc news, thank you for watching, and good night. Your front blows out, you go from having nice grippy rubber on the road and thats going to skid out and cause some serious injuries. Right now at 6 00, is someone targeting cyclists on the road . Tacks and nails discovered on a popular biking trail. Thanks for joining us. Taking the wrong tact to deal with cyclists. Tonight the chp is trying to find someone who dumped hundreds of small nails and tacks on a road used by psychiatrists. The tacks appeared to be strategically placed in the cracks on Kings Mountain road near woodside leading cyclists to think they were placed there deliberately. Reporter theres so many tacks in the roadway that they had to bring in street sweepers to clean them all up. Today cyclists are asking the person responsible to come forward. They are come down so fast and arent able to navigate the r d road. Lately riders have opinion warned by friends to pay close attention to the pavement. Its really frightening to be honest. Reporter grace and her teammates have seen pictures like this on facebook showing dozens of nails that were scattered near the summit on Kings Mountain road near skyline. On a